It looks like you could take GGT to the Santa Rosa Transit Mall, then take Sonoma Transit Route # 60 to Cloverdale.
The Sonoma Transit schedule shows limited service on weekends, a little better on weekdays.
http://www.sctransit.com/pdf/schedul.../090803/60.pdf
The general Sonoma Transit site:
http://www.sctransit.com
Several Golden Gate Transit routes go from Downtown SF to Santa Rosa. This webpage will allow you to see several numbered routes that make the (lengthy - 2.5+ hours) trip from SF to Santa Rosa:
http://www.goldengate.org/b/nov2Transit.htm
General site for Golden Gate Transit:
http://www.goldengate.org
Best wishes for your journey and skydiving adventure!