Quoted from Wilberto757:January/February and August/September are pretty good months. If you go on a Tuesday-Thursday even better!
We went January/February and one day was calling for showers. What a great day that was! Very little rain and the park was sparse. We literally jumped on and off rides. My kids LOVED The Simpsons and went on it over 5 times. That ride is awesome. Really all the rides are great. Kong was fantastic, the line up was long even on that day, but worth it. As others have said, Harry Potter rides are incredible. The line up for those are brutal. Get them out of the way early like others have pointed out. I'm envious. We have gone twice and would love to go again.