You should follow the advice of your family doctor or travel clinic on immunizations...  

When I first came to Belize and spent 4 months working in a clinic just outside of Punta Gorda, and was in the jungle 2 or 3 times weekly on clinic visits to remote villages, I did take chloroquine (for Malaria). Since then, during our 3 or 4 times yearly visits and during the past 5 years living here full time on the beach, we have not done any malaria prophylaxis, nor any Hep A, typhoid immunizations, etc. Maybe we are just lucky, but we also have not heard of a case of malaria here on the Peninsula in a long time. We don't know of any of the expats here (and there are a bunch) who do any differently. If you were working an archeological dig, spending days and overnights in the rain forest, then malaria prophylaxis would be entirely appropriate.

Also, we are quite compulsive about eliminating any potential breeding sources (standing water) for mosquitos on our property, as well as doing monthly spraying for pests, including sand flies and mosquitos. Along with the ocean breeze that we enjoy pretty much all the time, it's a tough life for mosquitos!