From the Luther Burbank Home and Gardens, take Sonoma Avenue all the way to Farmers Lane. Go left on Farmers Lane and continue until you reach Highway 12. Take a right on Hwy 12 and look for the turnout just past the speed sign. There's a little trail that begins right here.
Taking his cue, I shot the obligatory bike portrait.
The Santa Rosa Creek trail is a simple pleasure. It's right next to a busy thoroughfare, but it feels like it's in the middle of nowhere. It's a great place for riders of all abilities to enjoy some singletrack without dedicating a few hours to getting there, but it can also be the starting point for a big ride in Annadel, a burly climb up to Sugarloaf, or a nice road ride out to Sonoma.
UPDATE 12/7: Heavy rainfall over the past two weeks has destroyed large parts of the trail, and the sudden rise in the creek has washed ashore fallen trees and other stormy artifacts. Please wait until things have dried out a bit before exploring down there.