Are you sure "non-competes are unenforceable in California" generally refers to a different form where you agree to not work for competitors after stopping employment at a given company. If you use company equipment or company time, your work is subject to assignment to the company; I don't know how enforceable the clauses about competing fields with the company are, but usually there's a form to declare when you join (claim widely).

I should have been more specific. I was talking about the California law that more or less states that whenever you do work on your own equipment and time off, it's yours and not your employer's.