Can someone tell me when the Christmas decorations usually go up and when they come down?
It depends on when the holiday season at
Disneyland Resort begins and ends, and even then, some things do not go up right away.
In this thread - the
Disneyland at Christmas Time Superthread - Part 2 - you will find pretty much any information you would need to know about the holiday season, especially on Page 1, as well as lots of wonderful photos. In Post #3, you will see a Q&A section with commonly asked questions. That may be of some help to you. I will be updating the first page with news for this upcoming season as it comes in!
We are assuming that this year the holiday season will begin on either Friday, November 11th or Friday, November 18th. While
most of the seasonal decor, entertainment, food offerings and merchandise will be ready to enjoy, there are some food items and areas of decor that do
not come out until immediately after Thanksgiving. For example, Santa appears at all 3 hotels of the Disneyland Resort. But the hotels do not put up their decorations until right after Thanksgiving, so therefore, no Santa at the hotels until that time (though he will be at the Reindeer Round-Up in Disneyland and most likely in DCA as well), and no carolers performing by the hotel Christmas trees.
Also, certain food items such as tamales and the freshly made candy canes don't seem to appear until later in November.
So I would say that you can get 75% - 80% of the holiday offerings when the season officially begins, but you will get the full 100% of it if you wait until after Thanksgiving to go.