I'm with Uncle Dave. Nepethe is a must do. If you can work out a breakfast at the Sugar Shack on main in Huntington Beach it's worth a stop. Great food and great... um, sight seeing. Downtown Huntington is about as SoCal beach scene as you get. Not too overbearing like Newport or Manhattan Beach, but much more "torist accessable" than some of the other popular surf locations.
http://www.ci.huntington-beach.ca.us/visitors/beach_info/livebeachcondition.cfm
I'd probably try to do San Deigo to SF or even north of SF if you have time. There' such a broad range of topography that you'll pass through over a period of about 10 hours (driving time).
I'd recommend Las Brisas in Laguna Beach for lunch. It's on a cliff overlooking the ocean and it's an amazing view. A stop in Chrystal Cove between Laguna and Newport is really nice and there are beach side bungalows you can rent if you plan far enough in advacne. There's also a roadside burger joint (Ruby's chain but still tasty) right at the top of the hill.
Walt's Wharf in Seal beach and the whole downtown Seal Beach area is pretty nice.
Also, north of San Francisco, over the Golden Gate bridge is pretty awesome. You can go from the Marin headlands on up on PCH and its a pretty spectacular drive and fairly rural. Infineon raceway isn't far out of the way and Pt Reyes lighthouse is pretty cool. There's a guy up in SF who will take you out to the Farralon Islands so you can dive with great white sharks (in a cage) as well. I've done it, and that's probably one of the most memorable things I've done to date...
Good luck!
