Your 3/2 with a fleece rashguard (like O’Neill ThermoX) and good booties will get you through 90% of your sessions. On the other 10% - dawn patrols, mostly, with wind, 49* water, and 40* air, you’ll be glad you have the other one.
The 5 mil sections are mostly in flat panels so they don’t screw up your paddling too much, as long as the rest is like a 4/3. Its the 6/5 style suits for Nova Scotia, Great Lakes, etc., that aren’t useful in California.
water below point conception never dips below 50 degrees, and the weather is quite nice this time of year down here doesn’t start to get to cold until late december january