Water-related things are the easiest to do. A fun glass-bottomed boat trip to Shark Ray Alley (guaranteed to put you closer to sharks--nurse sharks--than you would ever have imagined) is fun. You can stay in the boat or go snorkeling. SCUBA diving is readily available as is sport fishing (reef, bonefish -- fly or spinning tackle). The trips to Mayan ruins are very interesting, giving you a chance to see the jungles as well as the small villages and some other resorts. Jewelry, especially silver and jade, is quite reasonable and beautiful. Food is delicious everywhere, and neither spicy nor expensive. Or you can sun bathe and swim in a lovely two-deck pool with a pool bar during the warm season. For reasonable prices you can rent any equipment you need for any sports you want to participate in. The restaurant in our resort was inexpensive but so good that people from other resorts came to Banyan Bay to eat.
Quick Tips:
Take mosquito repellent and medicines for possible upset stomachs. Bring lots of color film to photograph the many and varied species of birds and insects as well as the orchids growing both wild and in the trees in the resort.
Exchange rate is US to Belizian. ATMs won't work for U.S. banks. Visa and MasterCard only. Get US from local banks (as credit card advances). Good telephone service; access to the Internet from the resort. Don't take water taxis from Belize City to San Pedro; they're unsafe. Take a plane. Reservations must be made through the resort or at the airport after you arrive.
Best Way To Get Around:
The preferred mode of transportation is the golf cart (rentals about US/day). The roads are packed sand except for a small section of San Pedro which has small concrete cobblestones. The streets are narrow but the traffic flow is not heavy. When it rains, however, the roads turn into continuous potholes, and a taxi is recommended (US/mile). A fun place during the off-season, and reportedly a "moving" place during the high season.