As Gail notes, Brodies on the Northern Highway is like a small supermarket in the U.S., and it also has a pharmacy. In the Bel-Can shopping center (at the round-about) there's another fairly large grocery, Save-U. But a taxi is probably going to charge you US$20 each way from the international airport. There are three or four little groceries in Placencia, not as big as the ones in Belize City but they have most necessities, and you can also get fruit, vegetables etc. from Dangriga. If you really wanted to hit a supermarket in Belize City, you might think about flying out of the Municipal airport. You could take a taxi to Brodies', say, and then go on from there (less than 10 minutes) to Municipal. You save a little by flying from Municipal, though less than on trips to San Pedro.