Airline points depend on where you are from. United can bring you down from Newark and Houston. (35k for saver economy). American through Dallas or Miami. (30k for saver economy). Usairways out of Charlotte and delta out of Atanta. I have no experience with either on redemption.

Hotel points don't help you. No hotel chains that get you on the beaches of ambergris Caye or Caye caulker or Placencia, etc. Belize city has a best western or raddison...but you don't want to stay there. Check VRBO for condos and houses. Or check tripadvisor for one of the many nice options in local hotels.