I've only participated in one of their events, but have a friend who does them all the time and loves them. The only one I did was when I helped that friend run sweep for a 50k, and we had a great time.

They're well-organized and low-key. Generally all of them allow you to run various distances, and the routes often have spectacular views and very pretty trails. At least on the run I did, the folks we met were all incredibly helpful and friendly.

Woodside is about a half-hour south of San Francisco.

It could rain, so be prepared for that, but it probably won't. Also, it can be cold (well, what we folks here in the SF bay area consider to be cold, at least :^) In other words, if you're a bit of a wimp like I am, you might want tights, a long-sleeved jersey and maybe gloves. Or the weather could be beautiful and you can do it in shorts and a singlet.

Have fun in the bay area!

I did one of their runs for the first time 2 days before Christmas. I was so shocked to see how many people showed up (maybe 200 or so). Everyone was super nice and not competitive. The trails were well marked, and it was organized. It was a really challenging run, but they know how to select beautiful routes that make it so worth it. I did the 20k and hope to do a 50k with them at some point. Good luck on the run. I may do it as well.

I did three of their 50Ks in 2006, and they were all great. Wendell and Sarah, the owners of the company, are very cool and supportive. Their courses are well-marked (pay attention to the website and pre-race briefing to make sure you understand the system; once you have it down, it works perfectly), and their aid stations are well-stocked with all manner of good stuff. Enjoy!