Correction - we're driving from San Diego to San Francisco
There is alot to see. If you go up interstate 5, that will take you up fast, 101 is scenic, but bad traffic. I personally would avoid LA area, Ventura has a nice mission, as does Santa Barbara. Bakersfield is nice also.
Around Santa Nella is good,
If you have children look for Montery Bay aquarimarine.
Go to Auto Club and discuss what you want to see. Also go into the motels/hotels in your area and look for broucheurs.
No matter where you go it will be fast heavy traffic.
Go to the library, and look for Sunset Magazine. Lots of ads etc as the Coastal Mag also
Carmel, Monterey, Big Sur. Take the 17 mile drive in Carmel - it is fabulous.
I'd vote for the Monterey Aquarium even if you don't have kids.
Here is a link that might be useful: Aquarium