Two companies used provide a regular coach service from SFO to Santa Rosa, but the lesser one folded, no doubt blaming terrorists. Up-to-date details of transport of various sorts to the county of Sonoma are posted here: http://www.sonoma.com/visitorsinfo/transportationlistings.html and bus transport within the county is here: http://ci.santa-rosa.ca.us/tp/citybus/index.asp.
Nevertheless, coach out of SFO is an excellent way to reach us, and is the one we use and recommend. It is not too expensive and it is efficient.
The "Sonoma County Airport Express" company
(http://www.airportexpressinc.com/)
has a service from SFO that runs approximately every 90 minutes.
The pickup point is on the lower level of SFO, designated for
"scheduled services". (Marked with blue pillars near the old, domestic
part of the airport, and in the communal scheduled services bus area
at the new, international part of the airport, as of 2002.)
The trip typically takes a little over one and a half hours, two at peak.
There are several pickup points in SR for this company, and they change
periodically, so it is best to check.
As of 2003, the best one for us was no longer serviced.
It was a dedicated area near College and Mendicino,
and there was even a web-cam on their site to check it out.
Our house is closest to the Santa Rosa Avenue (Days Inn) pickup,
and Agilent is closer to the Sonoma County Airport.
The driver of the bus will arrange to call us ahead of your
arrival, so we can pick you up.
The cost is about US$24 plus
a couple of bucks for tips to the driver if he carries suitcases,
etc.