I know that everything is complete by the week of Thanksgiving but I think if I remember the posts from last year, decorations start going up in early November throughout the parks and resorts. I believe they start taking them down January 1.
We've been down a few times during the November 11th week. They have alot, if not all, of them up by then. I remember being so excited hearing Christmas Caroles when we were checking into BWVs.