Well, at the risk of giving you much more than you really want in the way of
info, here's a report I wroye on a trip two years ago:

Palau, the westernmost area of the Caroline Archipelago, comprises some 350
islands along a 400-mile northeast to southwest stretch. The major island
group is the Palau cluster made up of about 200 islands, only eight of which
are inhabited.  One of these, Babeldaop, is Micronesia's second largest
island (after Guam).  The island's capital of Koror is located just south of
Babeldaop; farther south the rock islands extend some twenty miles.  These
spectacular islets, shaped a bit like mushrooms, are topped by lush growth
and surrounded by calm clear aquamarine water and there are hundreds of
isolated sandy beaches.  Farther south still are the islands of Peleliu and
Angaur.  Peleliu was the site of one of the bloodiest and most futile
battles of WW 2.  The rock islands are limestone and the sea is eroding
their bases; my guess is that they won't be around in a million years or so
and you should go see them now while you still can.
Palau Pacific Resort is a swanky resort hotel spread across 64 acres around
a little bay with a white sandy beach.  It's about half an hour from the
airport and twenty minutes from the throbbing metropolis of Koror.  With 160
rooms and suites it's big enough to have the amenities you want without
being overwhelming.  There is a pool, two tennis courts, a spa, a gym, a
fishpond, a dive shop and boat dock and two restaurants.  The rooms are on
two floors and I suggest you ask for one upstairs and near the dock.  One of
the restaurants serves all day; there is always a buffet as well as a menu.
The other is their signature restaurant, which serves dinner only and is a
bit dressy; as Nick's idea of getting formally dressed is to put on shoes we
didn't go there.  The food was okay, but two weeks of it was more than
enough; we did try some of the restaurants in town but didn't find any worth
recommending.  In the evening there is a bus, which runs between some of the
hotels and restaurants from about 5pm to 10pm.  It's free and you can pick
up a timetable from the concierge.  Hard to believe that the local taxis let
that service get started!
If you stay in Koror a lot of the dive sites are an hour or more away.  The
dive boats get off the dock between 7am and 8:30, do a first dive in the
morning, pull in to a beach for lunch and do a second and possibly third
dive in the afternoon, returning to the hotel between 4 and 6 and for this
reason we did no sightseeing in Palau.  The alternatives are either a
liveaboard or you could stay on Peleliu, which is much closer to most of the
sites.  However with a non-diver in tow I was happy to be at PPR.
The on site dive op is Splash which caters mainly to the Japanese who make
up the majority of the guests at PPR.  We used Sam's Dive Tours; they picked
us up at the PPR dock each morning and whisked us off to their lair ten
minutes away.  There they have docks, boats, a shop, rinse tanks, gear
storage, showers, loos, and the Bottom Time Bar and Grill.  As well as
diving they offer kayaking, fishing, land tours and so on.  As in Yap, the
quality of your dive guide is crucial to having good safe diving, and I urge
you most strongly to try to find the right one for you.  After a couple of
hiccups we got Jonas, who is a star with years of experience on Palau and an
excellent attitude.  He really cared that we got good diversity, and he kept
finding rare stuff for us.  He was also meticulous about timing the dives to
coincide with the best current conditions; dive Blue Corner when the current
is weak or non-existent and you'll have a so-so dive, go when the current is
strong and you'll see why this site is so famous.  Most of the boats were
open flat bottoms with a canopy for shade and a couple of four stroke
outboards.  They were fast, but the long rides could be quite bumpy.  They
were not crowded, usually around six divers and either one or two guides and
a driver.  It's all drift diving and a typical dive starts at around 80
feet, becomes shallower and lasts as long as you like.  Almost all of our
dives were an hour or more, which we could not have done in no-deco mode
without using nitrox so unless you're a gas guzzler, in which case it won't
really help, I suggest you use nitrox to avoid missing good stuff.
I find it hard to imagine better diving than this; both the profusion of sea
life and the diversity of sites was extraordinary but in a way even more so
was the interaction between the different species of fish which could be
seen so clearly.  An example:  The Moorish Idols were schooling at Blue
Corner, something which only happens during a couple of months, so a cloud
of them blew here and there around the shelf; around them in a first ring
were the predators, trevally, grouper, Napoleon wrasse all trying to isolate
prey, then further out the shark cruised, waiting for opportunity, stacked
up like planes waiting to land at O'Hare, and in the distance those with
better hearing than me claimed to hear the porpoises.  On another occasion
we saw the same thing with a large school of scad.  We saw mantas on two
dives; the first we waited around a cleaning station at Devilfish City and
they came, just as in Yap, swooping around us, huge and ghostly and when
they had gone we, (meaning Jonas), found a couple of crocodile fish on the
bottom; the second the mantas were feeding near the surface and we swam up
to be near them.  There is an unidentified wreck known just as Buoy 6, a
100-foot Japanese fishing vessel at 65 to 75 feet which is heavily and
beautifully encrusted and there we saw a semi-circular angel, as well as a
bunch of lion fish.  I had my first experience of a down current; at the end
of a dive we drifted off the shelf into blue water with no visual
references, at about 70 feet Nick gave the signal to ascend and I kicked
gently to get going while watching my computer which said 70.75.80.85.  I
had some moments of sheer stupidity, my first thought "This can't be
happening", then, and I'm not making this up, "Perhaps I'm upside down and
kicking towards the bottom" and finally my brain woke up and said "Down
current" so I kicked hard up and away from the shelf and at about 90 feet we
came out of it and the computer started squawking about the ascent speed. I
saw my first giant clams, looking as richly upholstered as Victorian sofas,
creaking shut when touched.  Julie and Nick spent one day kayaking in the
rock islands and were very happy with that; I was down with a cold and didn'
t go.
I could go on and on, list the sites and the sea life, but it's all been
said so many times before.  Every single dive was wonderful.
Finally Air Micronesia, the original fly-by-night organization, loaded us on
for their 2:30am flight out and the journey home was just as long and just
as trouble free as the one going.

Random comments:

If I were planning the trip again I'd give Yap a miss; the mantas in Palau
were just as good and the rest of the Palau diving was so much better.  Sure
the life style in Yap was interesting to see, but still.  If you wanted to
combine Palau with another destination, perhaps think of Truk if you're a
wreck diver or maybe the GBR.

The currents in Palau can be very strong and can be unpredictable.  While we
were there another dive op mislaid a couple of their dive guides and
everyone's boats went to search; they were found, but only after spending 18
hours in the water.  If, like me, you are unsure of your ability to cope
with these conditions I suggest going with people who know what they are
doing.  Sam's provides safety sausages and reef hooks; you should take a
mirror and a noisemaker and, I suggest, a collapsible snorkel to stick in
the pocket of your BC.

We got sick.  I had a tummy bug in Yap; I had Imodium and Cipro with me,
which got rid of it quickly, but I still lost a day's diving.  All of us got
colds in Palau; Julie and I each lost two days because we couldn't clear;
Nick toughed it out.  Other people there had the same experience, no idea
why.

Make this trip: mortgage your house, sell your firstborn, do whatever it
takes but go.  You'll remember it forever.

The PPR is a beautiful place, but don't bother with a shore dive on their
"house reef".  It's dead.  And don't bother with their onsite dive shop
unless you're Japanese or you want to rent a tank to dive the dead house
reef.  I did, but even a couple pre-dive Red Roosters couldn't bring it back
to life.  Fortunately the shop had closed by the time I returned and they
never charged me for the tank.

Food is great there, some of the best on the island, but breakfast is
pricy - $14 for eggs, toast, and coffee.  You might as well partake of their
complete, but even pricier breakfast buffet.  Dinner has a different theme
buffet each night at the main restaurant, with a la carte available.  I
dined on the buffet with the president of Palau, so if it's good enough for
him . . .  The signature restaurant is incredible.  The best tuna sashimi
I've ever eaten.  The indoor bar is fine when you want your beer to stay
cold - they serve Red Rooster on tap, but get some at a store in town where
you'll find a range of bottlings including an awesome Mango Wheat - the
hotel actually encourages using the minibar fridge for your own brews so go
ahead.  The bar out by the pool is fun even with the grumpy bartender.  Ask
him for the local bar muchie instead of peanuts:  fried chicken skin in a
sweet hot sauce.  Your beer will get warm in 5 minutes, so drink up fast,
order another, and enjoy the music of a pair of Filipino guitarists who take
requests but prefer to mangle the Beatles with their bad accents.

As for skeeters, I don't recall any and bugs usually love me wherever I go.
The trades will still be blowing good in April, so you should be fine.  If
not, they sell bug spray in the stores and there's no malaria on the
islands.

No, but the salt water crocks might think of you as an hors d'oeuvre if
you wade into the mangroves for a nice little swim before/after diving.

Just kidding -- of course, mostly they run away.