decorations will be up. Generally they decorate for the holiday (Halloween or XMas) just before the first party. Halloween decs have been up since the beginning of September
Disney's Christmas decorations will definitely be up. At HS the Osborn Lights start getting put up I believe in either late Sept/early Oct. You will absolutely love the decorations, especially the Osborn Lights!! They are my absolute favorite!! It is hard to describe the feeling you get looking at them, they are just something that everyone should see at least once. My DH and I check out the different decorations at some of the resort hotels. Unfortunately do to my job I don't know when my DH and I will be able to get down there again to see the amazing Christmas decorations. Have a great time and enjoy.
Sorry, they're not planning to start this (lighting that is) until after Thanksgiving this year!
A lot of decorations will be up by the time you get there, but not all. We normally go during the 1st 2 weeks of December and are going mid-November this year - we'll miss some of the Christmas stuff, particularly at Epcot. MK will be decorated pretty much completely because of MVMCP. Enjoy