Good race to begin with?, SS good for starter? Train in Marin?

Sorry for overloaded title. 

Anyways been enjoying doing some more serious training on my road bike lately and wanted to try something competitive (read: organized, challenging) and fun. I prefer shorter faster efforts than endurance and did dabble a bit with 'cross as a teenager back in the U.K. (am 45yo now).

SS biked have an appeal and by the looks of things many of the courses around here are suited to it right? Been watching craigslist for 56-58cm SS but there's been nothing - guess I should've looked a month ago before the season started. Am also wondering if most people stick with canti brakes here since half the season is dry races? 

Last question has to do with finding places to train and I live in Corte Madera and bike commute to the City. Might be nice to use the 'cross bike as a rain bike - not sure how that works on SS though. Also for hitting the trails the gradients seem like they'd be hard on a SS bike. Are there flatter areas open to public? I've MTBed around Tam/Coastal/China Camp/Big Rock none seem like they'd be fun on a SS and sort of rough for any cross bike (esp. Coastal and Tam single tracks).

I plan on checking out Candlestick this weekend to see what the classes are like and whether this would be a good place to do a first race.

Thanks!

Mike.