I recommend trying Los Altos Hills, which is adjacent to Los Altos. Purissima Rd, Elena Rd, and Altamont Rd are parallel roads with low traffic that you can use to make lots of different loops. As you go farther west, the roads get more hilly.
If those are too easy for you, a really nice, but not real easy ride is Page Mill Road over the mountain and down to the ocean on the other side. Return via the same route or the popular Tunitas Creek Road (featured in the recent Tour of California race).
If you want a real easy ride, the Stevens Creek Trail in Mountain View (also adjacent to Los Altos) is pretty nice, except on weekends when it gets pretty crowded.
Last edited by johnny99; 06-27-10 at 11:33 AM.