While southern Cal may be warm, you'll be headed into some higher elevations where it won't be - could well be below freezing which could also mean snow.
We were in Death Valley two years ago in the winter and about froze with the low temps and howling wind. We had snow at the higher elevations. We were headed to the coast and thought we'd go through Sequoia, but they'd shut it down much earlier for the winter due to the early winter snows.
You might want to see the southern sights along Hwy 10, taking your time, and then come back through the higher locations in the spring before school is out and all of the families start traveling.
Also, what type of RV will you be using. It could make a difference for winter travel.
Bill
Nodwell RN110 out moose hunting. 4-53 Detroit, Clark 5 spd, 40" wide tracks, 10:00x20 tires, 16,000# capacity, 22,000# weight. You know the mud is getting deep when it's coming in the doors.