I could probably make an argument for any time of year except June through September. I'll never go during those times again - way too hot for us Northerners, and the frequent rainfall really put a damper on things for us. After many trips, we've determined decent weather is more important to us than crowd levels, so we generally will travel mid-Fall or mid-Spring. Late October is good for us because the intense heat has generally died down and its rarely cold that time of year. We've been in November when we've had to bundle up. And then mid-Spring, like early-mid April, is good because its not too hot yet but still warm enough to swim.