I'm not really very interested in u-turn tickets but yours sounds just like a dozen I've made in the last month, so do want to point out two important resources for you to use.
1. Fight Your Ticket, by David Brown. Every library has several copies.
2. West's Annotated Codes. Found only in larger libraries, or law libraries. You would look up the section you're accused of violating, and WAC will tell you all the cases that have been taken to appellate court. Xerox the pages and take them home with you. Look up the applicable cases on Findlaw.com. You're smart enough to take it from there.
I am also going to take this opportunity to ask you and all other CA motorists, to call your state senator or assemblyperson and ask them to vote against SB 57, which will add 40% to the fine on tickets. More details are available on the Action page of Highwayrobbery.net , the website about red light camera tickets.
NACOL