The diving in Belize was excellent. Lots of coral, beautiful fish, pleanty of morays, nurse sharks etc. The diving was just offshore 10-15 minutes from the dock--excellent.
We stayed at Victoria House. True luxury. Most of the boats took us out for two tanks in the morning. They brought us back to the dock for lunch at the resort with an optional two more in the afternoon. I'd step off the dock and order room service in my wetsuit. As soon as I'd showered and dried off I could eat lunch.
I highly recommend Bradley's. Its a small operator with a little boat run by two brothers. He took us with as little as two divers. He is very very safe and flexible with great service. His family has been doing this for decades.
I did two big trips, one to the Blue hole and one to Turniff Atoll. I recommend doing both of them with Amigos de la Mare (I think they are the biggest dive operator on Ambergris). They were both excellent, three tanks and all day. The blue hole was fun, but only worth one dive. It was very deep 140' with interesting formations and LOTS of sharks. The trips took us to two other reefs that day and a lunch stop with a walk through the jungle to a booby preserve.
The mosquetos can be fierce after a rain--getting better after a few dry days. San Pedro seemed safe enough but it was a bit of a squalor. Poverty was extreme. I was there for diving and relaxing so I only went once. We took a trip to Walkers Key and it was much nicer for shopping around. The resort restaraunts were nice.
We also did two non-diving boat trips that were fabulious. We went birdwatching, shell collecting on remote beaches and snorkelling at a reef. It was just our family in a small boat and we went to serveral little islands. Annother trip was mananatee watching, lunch and snorkel on a sandbar, then WAlkers Key and snorkelling at stingray alley. Terriffic!
My only complaints were the mosquetos and that the beaches were poor. They don't really have sand and the water is filled with sea grass. Not great for kids who want to play on the beach/water and keep getting bitten. No snorkelling except by boat. Also, bring all your gear--you won't find any dive or photo equipment for sale on Ambergris.