Having ridden my bike across the US, there are only 2 places I've found (but I haven't been to CA yet)

Asheville, NC - Amazing road biking and mountain biking. For road riding, you can ride right from town, or if you go north 20 minutes you can do 80 mile rides in the mountains and see less than 20 cars on flawless blacktop roads.

Traverse City, MI - No mountains, however there are tons of hills and tons of incredible views of the lakes. Biggest downside is winter