Like many other cities and towns, Ambergris Caye's restaurants and food prices vary widely depending on the shop and the season. There are a plethora of delicious and incredibly cheap food options on the island, including street food and locals' favorite spots. In Central Park you'll find cheap food stands that offer everything from burger to burritos for around $5. You'll also find authentic Belizean food at Boogie Belly's on Middle Street for under $5. Fruit and vegetable stands line the streets and offer great prices - don't be afraid to negotiate the price with the stand owner either!
While there are also plenty of higher end restaurants, I would venture to say most of the restaurants on Ambergris Caye cater to a price point somewhere in between. Groceries, however, can be a mixed basket. Since the island imports most of its dried goods, some food will be decently priced and others will be staggeringly high simply because of the cost and weight of the item in relation to the cost of import. However, you'll learn quickly which goods cost more than you'd expect, such as nuts, and be able to adjust your shopping list.
(Food taken out and eat at Grand Baymen, Ambergris Caye, Belize, pictured.)