Some Answers and Suggestions
Velkommen! Welcome aboard the RoadTrip America Forums!
That general RoadTrip comes up quite often, so the first thing I'd suggest is that you read through some of the previous discussions of similar trips. Typically, the California coast has what is called a Mediterranean climate and even in winter it never gets all that cold, and the desert southwest is actually quite pleasant for much of the winter although there is the chance of occasional light overnight snow. I very much enjoyed my visit to the Monterey area and would strongly endorse your plan to spend at least one night there. But I'd also strongly recommend that you take CA-1 down the coast rather than US-101 to Los Angeles. The other stop on the way to L.A. should be in the Cambria area; it's pretty close to halfway and has a few choices for lodging.
AZBuck