The main pool closes early, either 10:00 or 11:00, but the quiet pools are open 24 hours. My DS and I would frequently take a dip at 12:00 AM after coming back from the Kingdom,and it was GREAT!!!
I agree the closing time is 11 at the big pool but I remember last year coming in from DD and still seeing folks in the big pool after midnight so i doubt its a time they really keep......but the smaller pools are open 24 hours but they also do not have lifeguards either.....