We went this year May 9 - 16. It was really great. Crowds were light. Oh, there were places where the crowds were heavier, but we did walk right up to all the rides. The heat was ok, but about mid afternoon, we started to feel the heat. Really enjoyed walking into shops that had those fans that blew cool air straight down!!!!
We enjoyed the May trip so much, we're going again next May - first week. We've been in December (we'll try the first week if we do December again), and October (which is my favorite time so far)