Well, I think the first MVMCP party is Nov 7th, and Osborne Lights start the same time I think. So they should be at least be up in many areas, I think, when you go. I haven't been in Nov for a while as we go early Dec now, but used to go mid Nov and as I recall, many decorations were usually up by then! One thing that won't be up is the big Xmas tree in MK. They don't put that up until right after the taping of the Xmas parade, usually the same weekend in Dec(Dec 5 & 6 this year).
We've been three times for Halloween, they start decorating the park the day after the last Halloween Parade, which is usually Nov. 1st or 2nd, haven't looked when the last one is this year. They put them up really fast