Early Thanksgiving week is bad, at least from my experience and what others have said. Thanksgiving Day, Friday, and Saturday are not as bad.
Yes, this is what we found. After all of our
Disneyland trips (going about 3 times a year for the last 10 years)--our most crowded trips were:
Thanksgiving week: Monday thru Wednesday BEFORE Thanksgiving (this was the most crowded I have ever seen the parks--it was impossible to even move from one area to another and beyond all reason).
Spring break: The week just prior to Easter, but avoiding the holiday. Again, similar crazy crowds (with threatened park closures due to masses of people). If you go a few weeks prior or after you will be fine, but he closer you get to the actual holiday, the worse I believe it gets.
We typically go once or twice every summer (usually June and July), and those are crowded, but in a very summer crowds crowded way. So not over the top crowded, just busy.
I personally love going in the summer. Full schedule any day of the week with great fireworks weather.
I personally will never go Thanksgiving week again, since it was so crowded for us 2 years ago. The memory lingers! I know that if you go Actually on Thanksgiving day and beyond it is much better, but I like to be home for Thanksgiving, not at Disneyland.