+1 to what missjulied said re: riding on hills behind slower, inexperienced riders, walkers and car traffic...

This is a great ride and has rightfully been noted as a classic American bike ride in Bicycling magazine, so it's gotten bigger and bigger each year, but that's all part of the experience. You have everyone from area club racers to families taking their kids on tandems or in trailers, and there are lots of folks who haven't done rides with crowds yet so it's best to keep an eye out in front of you while also being alert for 'silent passers' - some even trying to pass on the right - ugh! Model the behavior you want as in, calling out as well as using hand signals, when possible (not always easy to signal when in the thick of a crowd, crawling up a hill or starting up from a traffic light, but calling out "slowing, stopping, or rolling" is always helpful to others nearby), point (or call out) hazards in the road, when you spot cars at driveways or cross streets too).

There is a rest stop with cider and baked goodies as well as a finish line festival; I also have enjoyed 'recovery' chili and beer at the Winslow pub before hopping back on the return ferry
I've attached the link with the details of the ride - route, elevation profile, ferry schedule, etc here from the event host, Cascade Bicycle Club. This has been the opening ride of the cycling season for 30ish years and so there is a ton of helpful information available. http://www.cascade.org/EandR/chilly/CH_details.cfm

I'd suggest that you not wait until then to register as, lots more riders wait until the morning of to see how the weather is and when we've had glorious weather, we've actually maxed out @ 5-6k registrations.
Also, try to lean your bike upright on the ferry and not flat on the car deck as I've seen riders trip while threading their way across the deck through lots of bike to get to the stairs, and the last thing you want is someone's foot mashing your spokes!

Tailwinds to each of you for a safe and great ride with lots of fun throughout.
Mary