There's not much tubable public water in Petaluma that I know of. However, you'd only be 30 - 35 minutes from Spring Lake & Fountaingrove in Santa Rosa. There's also Roberts Lake in Rohnert Park, which is even closer to Petaluma & right by the freeway. I've never tubed it, although I've heard it's allowed & that it has some big fish in it.

I have to tell you, though, that if you run to Santa Rosa between 4 - 6 PM to fish, it could take over 45 minutes because the traffic is such a mess.