7, but redwood national park is just too far. All without traffic of course.

Kings Canyon Sequoia Yosemite Lassen Volcanic Pinnacles Muir Woods Point Reyes

Even ignoring traffic, you are counting the same park multiple times. Kings Canyon, Sequoia, Yosemite, Lassen Volcanic, Pinnacles is not bad but it's not 8.

https://en.wikipedia.org/wiki/File:NationalParks.forwiki.pdf

https://en.wikipedia.org/wiki/List_of_national_parks_of_the_...

But, Muir Woods is part of Golden Gate National Recreation Area and Point Reyes are not separate parks.

Two more national monuments I did not know about. Not parks. Was fun to see what's near by.

http://www.blm.gov/ca/st/en/prog/nlcs/California_Coastal_NM....

http://www.fs.fed.us/visit/berryessa-snow-mountain-national-...

Don't forget Henry Coe State Park.