Took a similar trip from Napa to San Diego in April. With all the pull offs on the ocean side, it just seemed easier to stop and look. I like the piers in Santa Barbara and Santa Cruz. You can get real close to the sea lions at the Santa Cruz pier.
Yosemite was a little off the path but well worth it.
If you are going to Marin County, a tour of the Nike Site was really special. I think it is the only reconstructed Nike Site in the US.