Petaluma is famous for welcoming new comers and tourists. Heck, we welcome EVERYBODY! Unlike the streets of big cities and, of late, Europe, eye contact on the street is encouraged and greetings are common and appreciated. Why not smile and wish someone a good day?
Like many other California towns, Petaluma has its own locally produced sidewalk art. Since American Graffiti was filmed here, the theme is old 1950s and '60s cars. The variations on this theme are very creative. It's fun to just go around looking at them.
People are typical Northern California. They are generally nice and open minded, but sometimes centered on themselves. For out of country people: Typical U.S. tipping and greetings and cultural beliefs.