My favorite time is Columbus Day week. Very low crowds. I think parents hesitate taking kids out so close to the beginning of school. Also, I'm not sure that Columbus Day is a National holiday. Although, this I am not positive of. We have gone a few times this particular week it has always been in the high 70's to mid 80's. We have even experienced it in the high 80's to mid 90's although we were told that was a heat wave, and very unusual.
good luck