Bicyclists should not be riding on these roads, period. These roads are extremely narrow and have many sharp blind curves. To compound the issue, motorcyclists use these roads as raceways up to and down from Skyline. Just drop by Alice's Restaurant on Skyline to see them.
I have lived with Page Mill Road as my backyard for 30 years. I rode my bicycle on Page Mill once and deemed it too dangerous and will never do it again (the part near 280 to Alexis, which is not as dangerous as the parts further up toward Skyline).
Most of the bicyclists ride in a manner that is extremely dangerous to themselves and to motorists. There are plenty of bicycle-friendly streets in Palo Alto, such as Bryant, where bicyclists should ride.
When did bicyclists lose their sense of well-being, place themselves in danger and blame others? If bicyclists want an uphill challenge, they should ride one of the advanced bicycles at the gym.