In San Pedro
Seafood is, of course, the most popular food on the island, and there's plenty of it around all year. However, please keep in mind that there are seasons for lobster and conch (because sea turtles are endangered, never order turtle). Officially, lobster season runs from July 15 to February 14, while conch is available from October 1 to June 30. Local restaurants and fishery officials have struck a deal to allow lobster to be served in the off season. Supposedly this is lobster caught and frozen during the open season, and not while they are mating in the formerly closed season.
If you're staying for an extended period of time, or have a room equipped with a kitchenette, you'll find several good markets around town. The largest, most modern, and best stocked of these is Island Supermarket (tel. 226-2972), located on Coconut Drive.
Finally, since it doesn't fit into any of the following locations, you might want to try Blue Lotus (tel. 610-2583), which serves up Indian-inspired fusion cuisine on an open air spot over the water across the lagoon from downtown San Pedro. Call for a reservation, and they'll provide free water taxi service.
Inexpensive -- Jambel's Jerk Pit (tel. 226-3515) is located right on Barrier Reef Drive, and serves up the same excellent Caribbean fare you'll find at its sister restaurant in Belize City. Ruby's Cafe and Celi's Deli, on the ground floors of Ruby's hotel and the San Pedro Holiday Hotel respectively, are good places to pick up a light meal, and both specialize in fresh-baked breads and pastries, and sandwiches to go.
Other dependable options include Micky's (tel. 226-2223), which is a popular local joint, Caramba (tel. 226-4321), which serves a mix of Belizean, Mexican, and Caribbean fare, and Ali Baba (tel. 226-4042), which specializes in Middle Eastern cuisine. For a seafront seat in the sand, it's hard to beat Lily's Treasure Chest (tel. 226-2650), which is great for breakfast, lunch or dinner.
On North Ambergris Caye
Despite its relative isolation, the northern section of Ambergris Caye has perhaps the island's greatest concentration of truly excellent eateries. If you're staying in San Pedro or on the southern half of the island, you'll need to take a water taxi. Most of these restaurants will be able to arrange this for you, usually at a reduced rate from the going fare.
I've been hearing good reports about another new contemporary fusion-style restaurant, with a heavy Pacific Rim influence, called Pinki Knox (tel. 622-6991), located a little bit north of the bridge.
Note: This information was accurate when it was published, but can change without notice. Please be sure to confirm all rates and details directly with the companies in question before planning your trip.