Due to the road condition, I can't give this a better rating. The grooves will catch your tire through some turns. It is rough, all the way. I also bicycle this road up and will not go down it is in such poor condition. Probably good with a wide tire bike or heavier bike than mine GS500, but not so good on mine.
Yerba Buena road is easily reachable from PCH. Its past Mulholland in Ventura County.
This road is a Butler G1 road. At the end, you can opt to run the Snake at Mulholland, come down Decker Cyn, or go to Westlake blvd and then the 101 fwy.