I have been early in September both in 2001 and 2003, and the crowds are very low. Most things during the week are walk ons or only a few minute waits...Weekends the parks are a bit more crowded with local people touring....Go and enjoy it is a great time of year to go..
Was there week of Sept 7-12th...crowds were very low, except on sunday the 12th they seemed higher, but normally are on weekends due to local folks visiting too....have fun!!...