There are a couple spots. I used to go out when I had my old boat. Cant bring myself to put my 210 in there. There are 3 free launches that I know of. One is out in Kennedy park, one downtown past the library and another out at moors landing out in los coneros on cuttings warf road. I have ridden petaluma river, the delta and the napa river. The Napa river is not that bad. It was alot of fun.
Here are some pics of the river and where we launched from.