The Pacific Coast Highway (Highway One) runs the entirety of the state, almost, and is beautiful...minus a very few short stretches. There are plenty of cars to contend with, but it is a famously ridden route, and all locals are used to sharing the road. I highly recommend it no matter what part of CA you're in. If you don't have a bike just drive, but you can rent a bike from just about any bike store near the coast if you want.