Lily's Treasure Chest is on the beach at Lily's Hotel - a few doors N of Fido's in town. Good food, pretty cheap prices, Belizean service

Great people/fisherman/working folk watching spot.
Street vendors are great. I like Shirley's (about the 3rd or 4th in from the street) but all are busy and popular with the locals. I try not to eat anywhere there are no locals eating! If the place is full of tourists and the only Belizeans are working there - you know something is wrong (too expensive, bad food, "questionable" owner or operations.