I'm in the same boat as you. I'm thinking about pulling the trigger on one of these:

http://www.realcyclist.com/castelli-sottile-jacket-mens


Rode yesterday, 64 degrees, slight drizzle throughout the ride, started coming down more for the last 15 minutes of a 2 hour ride. I only had on a Jersey, short-sleeve baselayer, gloves and skull-cap up top. My arms were completely open to the elements and I wasn't cold at all. I only wished I had on arm-warmers, I think a light water-proof jacket with different layers could take care of anything in Cali.

^That Sugoi looks really nice too.