Tony, I now several people who cave dive in Akumal two or three times a
year and love it. Not being a cave diver, I have no personal experience.
 I can get you more information if you are interested.

Cave diving in the Mexican Cenotes is much easier than some other places.
Keep that in mind -- realizing that a course in Mexico may not teach you
all the skills you need to survive central Florida's caves.  At least not
without some additional instsruction of supervised experience.

That said, I have used the Akumal Dive Shop http://www.akumal.com
for a guided cenote dive.  This was a guided dive, not instruction.
(We are "cavern" certified.)  They seemed to operate in a safe manner
and took an interest in us and our questions, etc.  Our divemaster
was Frida (who is Italian).  She is also an instructor; I would
recommend her.

I just got back from Akumal, and the diving was awesome. I am familiar
with the Akumal Dive Shop, but I do not know who is teaching cave
classes there now. Freida is no longer there, and recently had a baby. I
did a couple of dives with her husband (Nick Toussaint)last week, and I
can highly recommend him as an instructor (he was my trimix instructor
several years ago). There are many other good instructors in the area.
If you lean towards DIR, Nick is excellent but not religious (and is
probably the best all around diver I know). Drop me an email if you want
his contact info. Zero Gravity Diving is the GUE/Halcyon shop. I only
met one of their instructors briefly, and he was very pleasant and
helpful at a dive site. If none of this suits you, drop me an email and
I can steer you to someone else. you can also search for instructors in
Akumal, Playa del Carmen, or Puerto Adventuras.

to get to Akumal, you fly into Cancun, and drive about 100 kilometers
South. There are many places to stay there, from very inexpensive to
luxury. It is central to the most popular caves. We stayed in a beach
bungalow at Hotel Club Akumal Caribe Villas Mayas, and it was $66/ night
and had everything we needed. The rates very with season of course. Most
shops/instructors will provide tanks and whatever else you need, as well
as transportation to and from the cenotes.

I don't recommend going there in the summer. IMO, now is the best time.
Dec 20 through April is the high season, and after that it gets really
hot and humid with lots of mosquitos.

HTH
al