I would consider passing a town ordinance that mandates single-file riding on all Portola Valley roads and installing Bike Single File signs on Alpine Road, then citing people who ride two abreast or talk when they ride or ride with headphones.
I would also ask the sheriff to cite bikers for any violation of the California Code (http://www.dmv.ca.gov/pubs/vctop/vc/tocd11c1a4.htm) or breaking the speed limit, unless they have a permit.
I would consider exemptions for pelotons or competitive cyclists (we need our Olympic medals) if they have a permit (could be issued for a year) and they have a car or bike in front with flashing lights just as one would have for a wide load. One could consider having a car behind, but I don't think this is necessary as there are already rules for crossing the double yellow line if cars try to overtake a crowd.
This is what I mean by defensive cycling:
1. Stop at all stop signs.
2. Signal before you turn.
3. Always ride as if your bike is a vehicle, not a recreational, toy and obey the California Code.
4. Always be aware of sounds like a sneaky Prius that may be in electric mode and come close without you hearing it.
5. Ride with a rearview mirror or be prepared to look behind so that you are always aware of what is behind you. A fast bike that comes too close may be as bad as a car.
6. Don't swerve or stop for squirrels.
7. Expect cars to cut you off and don't try to beat them.
8. If cycling past a parked car look for people inside it, look for reversing lights or indicator lights, and make sure you have room if a door opens.
9. Navigate the cracks — there are some near Ford Field on Alpine Road — and if you have skinny wheels know how to cross a crack or avoid it entirely.
10. Keep your bike well-maintained with good tires, properly inflated, check for loose nuts and bolts, make sure gear wires and brake wires are anchored properly.
11. Wear bright colors with noticeable patterns so drives can easily see you on the road.
12. Wear appropriate gear, including a helmet, and don't let shoe laces or trousers get caught in the chain, etc.
13. Never go so fast that if a deer jumps out at you you can't stop. I've had deer jump off the path opposite Roberts from high up and come out just below Ford Field. They are worst in October when they rut.
14. Beware of dogs on long leashes, children playing with balls, skateboards, scooters and pedestrians who may come in front of you. Always think where you would go if they did.
15. At every driveway listen and look for cars coming out.
This list may seem pedantic, but it comes with over 40 years of experience biking on roads. Have fun and safe cycling.
Alpine Road, Portola Valley