I stayed at Paradise Villas, just north of the town center--technically still in San Pedro but a 3-5 minute walk to the town center. Paradise was really great. Full kitchen (fully stocked with kitchenware), living room, dining area, bedroom and bathroom. Like home away from home, but with daily cleaning service. Very decent pool, with a great outdoor shower--I showered daily al fresco (something I like to do; I don't over analyze it ;-). A resident cat or two or three meowed at my door each morning. The property is very convenient. Literally outside the back door (opposite the beach) is a nice fruit and produce stand. Walk a few dozen paces to the right and there are two supermarkets. Immediately to the left are two very nice delis; Mathieu's has excellent bread/baguettes. Nothing is far from anything on foot, though. It's a manageably small place. The golf carts buzzing around town I sense are mainly those people living outside San Pedro, farther north and south of town.
I dove with Reef Adventures, whose shop is on the dock that is almost immediately outside the front gate of Paradise. Ridiculously convenient. You can keep your gear at the shop (I kept everything there except my regs and computer and mask), though you wouldn't have far to walk with your kit if you wanted to keep it with you. They do everything for you, including rinse your gear. When you show up in the morning, your gear is rigged up and on the boat. Ched is the local part owner, Capt'n Ron the itinerant American one who resides in Oregon when not on Ambergris. Mike was our guide on all outings--he's a laid back and easy going Belizean, but cooly contientious (he sits in for the chicken if it fails to poop; he announces where he'll be drinking each night, hoping you'll be there too and take care of your guide; he welcomes any and all complaints, esp those written on a hundred dollar bill--maybe you can imagine the likeable vibe you get from Mike). Chucky was our boat captain; he also took me and my wife snorkeling and fishing. Small operation, but I kind of liked that, esp when I saw the party boats (Amigos, Ramons, Ecologics) buzzing by (but if the winds kick up and wake the waves and you get sea sick, then you might appreciate a larger boat).
I dive my most advanced gear when traveling--MK20UL/G250, Scubapro backpack/DR travel wing, old Aladin sport computer (here at home I dive MK10s and adj 109s). No Nitrox, and I'm pretty sure Reef didn't have any (but I'm guessing Reef's tanks are filled elsewhere and I don't know if that fill station might have Nitrox). What's an analyzer ;-)? I might note that I wore my 3mm fullsuit plus a 2mm vest in the 82 degree water off Ambergris, and, as usual, I was shivering after 25 minutes. Almost everyone I dove with was a freak who wore a t-shirt and board shorts, or at most a very thin neoprene rash guard top. Next time I go to Ambergris I plan to bring my TLS350 and Polartec underwear.