I once flew from Duluth, MI back to Palo Alto, CA (really close to OAK)
and we crossed the Sierra from Reno (KRNO) via Truckee (KTRK) and you
can then follow I-80 and V-392. It was during the summer, though, with
high density altitude. We circled forever to get out of Reno and up to
around 10000ft. The cold weather in the winter will help big time.
Beware of the winds across the mountains, though, they could ruin your
day :-). Also, wouldn't advise IFR in a 172RG there.

To the south I can only suggest the following route: desert, desert and
more desert and V12 to get to General Fox (KWJF), fly over Gorman VOR
(GMN) and follow V137 north. Avoid Tehachepe pass (not sure if spelled
right). It's a low section between roughly KWJF and Bakersfield (KBFL).
It's tempting, but a friend of mine had to turn around because of high
winds and severe turbulence there a while back and he will never try it
again. On a windy day Gorman VOR might not even be a good choice. My
friend ended up taking a route over Fillmore VOR (FIL) and up the
coast. The coast is beautiful if you have the time for the small detour
by the way.