I’ve been riding for a few years in the east bay. Never ridden with or even seen anyone else riding on either street or trail.
I’d love to meet up for a group ride sometime. Hopefully not for anything too hard. I’ve ridden Mt Diablo, and sometimes I ride easy trails in Joaquin Miller or Briones parks.
Hey!
I’m coming over on June 16th to live in Burlingame for a year. I’m going to take my 20" trials with me. Would be great, if we could meet up for some riding/hopping! 
We have two mailing lists for greater bay area riding:
http://groups.google.com/group/unicyclists says “Santa Cruz Muni” but it’s not limited to Santa Cruz, nor is it limited to muni… it’s just what we like to do the most 
http://berkeleyunicycling.org/ is for east bay riders to talk about unicycle basketball… and the occasional muni ride.
Sign up for both and you’ll be riding every weekend!