I think the DLR website says somewhere that this year's Halloweentime will last from September 25 - November 1. That means that everything Halloween-related will be up and running on by September 25 and then they will start taking everything down on the evening of 11/1 when DL closes (which is a Sunday). Then the Christmas decorations come out. If the Haunted Mansion Holiday happens as usual this year, it will stick around from 9/25 all the way to early January. The crowds will probably not be TOO awful in those last days of September, but they will get worse after that because Gay Days, Utah Conference, the Trick or Treat Party and other things will bring lots of visitors to the parks as October progresses.