I'm from Sonoma County; moved away 30 years ago. I've lived in Sonoma Valley (before it was fancy), Santa Rosa central & Roseland, Sebastopol, Camp Meeker, Monte Rio & Guerneville. Hands down, I love East County. The Russian River (not Healdsburg) is my all time favorite. I wasn't a fan of Santa Rosa even tho' I grew up there & lived there & on the River until 1991.
The River may not be as ethnically diverse as Petaluma (not a fan), but the people are open and not full of $hit. The wonderful gay invasion of the 80's drove out the bikers & brought prosperity & diversity acceptance. I'm not gay myself, but was treated with so much love & respect ... I felt like royalty there.