Thanks for the comments so far, keep them coming
2 additional questions:
1. From San Fran is it worth flying to Reno or am I better off just driving? I think drive, also so that I have the car to get around the Tahoe area. What is the difference in time?
2. How busy are Squaw and Alpine going to be just after New Year (considering that it is still mid-week, Tuesday-Friday)?
I would deffenetly drive, its about a three hour drive from san fran, and if you flew into reno then drove to tahoe its probley about 45 min or so.
The week between christmas and new years will be a lot busier than after new years, you will have better luck going that week after, but its tahoe, they still might be some people lingering around on vacation still, but mid-week will be better than the weekend.