We're just back from ten days on AC and there were LOTS of places to purchase basic groceries. Fair warning, though, especially if you go to the groceries that are clearly more tourist-oriented (like the Island Supermarket across from the beer/soda distibutor) --- the prices are MUCH higher on most things than you may be expecting (like $18 Belize, $9 U.S. for a box of cornflakes). If you MUST have your cornflakes, Cheetos or Pringles, bring them from home in your luggage. If you're on the south end, look for Marina's Tienda (near Riverview Gardens and across from Antojitos Santelmo). The prices were much more reasonable on every product (including the rum!).