The mood is upbeat and fun at Bella, a family-run Sonoma winery where tastings are conducted inside the barrel cellars, within giant caves dug out of the hillsides. With vines on the estate dating back more than a century, here one can experience the luxuriously concentrated flavor for which old-vine grapes are prized. All of Bella's reserve-vineyard, small-lot syrahs and zinfandels have a...