Have you considered Caye Caulker instead of Ambergris Caye? Caye Caulker is definitely more funky than Ambergris, though Ambergris has the more upmarket resorts (which sounds like you don't want anyway). We stayed on Caulker, but did a day snorkelling trip and went to Ambergris, and didn't like it as much. Even if you don't dive, don't miss snorkelling in the Hol Chan Marine Reserve.

Dianne in a not so sunny Sydney, Aust