Considering that in my life I've been on:
April Vacation Week
Christmas Week
I'd say that the 1st week of December is great. DH and I went in 2007, from Dec. 2-7. We did have some interference with the Pop Warner crowds, but as mentioned on another recent thread, it's really NOT that huge of a deal.
So, when we went, I found that for the most part, we were able to walk right on the rides, or wait minimally (15-20 minutes). I was amazed that that was possible. I think the longest wait we saw posted was 40 minutes!
The weather was actually really good -- about 75 degrees for the most part -- one day was maybe 82 -- but the nights were cool enough for a sweater/light jacket.
I loved the Christmas/Holiday vibe, and I'm looking forward to going at that time again!