eberjef,
like yourself I am a new member here also. If you live in marin county, a couple of hours driving can put you on many Tenkara perfect waters. Day trips or overnites. Putah Creek as was mentioned earlier, altho I usually avoid that creek. The foothills of the Sierra's are full of small streams, some only worth it in the spring, others into the summer, and still others fishing good all thru the season.
If you head north up the coast, many opportunities open up. North up the Sacramento valley to Redding is another whole group of rivers. You can PM me if you want . I can list them for you or just provide basic info. One important thing to remember is to be willing to do a little research with a road atlas/topo maps, pick an area that appeals to you and your fishing wants, then drive there and explore. That is the main way I discovered my own favorite streams, many of which I return to frequently. Even if you get skunked, you can learn many things. If the stream looks to have potential, visit at another time and then make decisions. Sometimes you can be very surprised.