I can speak of a couple central coast courses, after the Santa Cruz/Monterey area, the next worthwhile course I know of is Waller Park in Santa Maria. One of my favorite courses of all time, 27 holes in a really nice park, great tee pads and baskets and a good variety of shots. A lot of it doesn't even look like you're in California, looks more like North Carolina with pine trees and (green) grass and sand. Great course, but you might want to follow some locals, as 9 holes were added to the original 18 and it can be easy to miss the turn to hit the extra 9.
Santa Barbara has my original home course or Goleta to be more precise. It's a cool little course, but after playing more courses since, I've realized it's pretty much a pitch & putt course. I haven't played Juel Park here in the Seattle area, but I'm thinking its probably along the same lines. Might be nice to play if you want to take a pit stop, but it's certainly not the most noteworthy course in CA.
Inland from Ventura is a great, relatively new course at Lake Casitas. It's on private property around a reservoir with camping and fishing available. I think it's like $6 per car to get in, but it's well worth the money. I guess the local pro level players were discouraged at not having a course around that was challenging enough, so they all pitched in and built this one up. It's an awesome one that'll test your skills for sure. Great elevation changes, some water hazards, and some downright phenomenal southern CA vistas.
Though most of the courses shown here are probably not on your route, you can see some cool slideshows of courses CA courses here (including the 3 I just mentioned) http://www.pickyourdisc.com/CourseSlideShows.htm
Only other courses I've played in SoCal are Sylmar and Morley Field. Sylmar is all right
, but nothing special. I wouldn't recommend going out of your way to get there. Morley is pretty cool, but pretty much being the only real course in San Diego, it can get crowded. Really well maintained though, and I believe 5 different pin positions on every hole which get changed every Monday.
Haven't played it, but from what I hear La Mirada is a course that must be played if you're in LA.