Check out this site.... If you find one add it to the comments.
Working for a bicycle-friendly, greener and healthier San Francisco since 1970
A new rider takes off at SFBC Family Day.
Through day-to-day advocacy, education, and working partnerships with government and community agencies, the SFBC is dedicated to creating safer streets and more livable communities for all San Franciscans.
Our active 9,500 members represent San Franciscans of all ages, from all neighborhoods, who are working towards more safe, efficient, and green ways to move around our city.
more here http://www.sfbike.org/