Avoid the height of the hurricane season. Even if you manage to dodge a tropical storm, the weather is just mushy. Rain for a half hour, sun for the other half hour. Continous cycle like that throughout the day.

Still, in my week-long visit (this was about 20yrs ago), I got the sense there was much to see and do and I did luck out with one full sunny day at the beach (ahhh!).

Oh, and watch your wallet.