If I'm enrolled in a CSU during the fall, and a CC during the spring, what will a UC see?

The trouble with transferring in one year is that you will have to complete both general education requirements and prerequisites for your major. Taking another year may help you decide what you want to do.

If you want to apply now, though, it definitely won’t hurt to complete IGETC by the Spring (if you can). That will set you up nicely to take whatever you want next year, if you don’t get in where you’d like.