If you are a responsible driver and just tasting in the Sonoma square, you have many tasty options. Adobe Road and Charles Creek have small production yet bigger varietals like cab and zin. R2 has Rhone varietals from the best places in California. Walt is for Chardonnay and Pinot Noir lovers who really want to see the diversity of these grapes.
But a favorite will always be Eric K James. Tucked away in an alley but certainly not quiet. On Friday and Saturday nights they stay open late and play New Orleans style jazz. Their winemaker/operations/tasting room host makes your time there fun and is always interesting to talk to. His wines are all well crafted and represent the ultimate typicity.