There is actually a winery (two, to be exact, but I only visited one) on Pleasanton Ridge, a southern section of the Berkeley Hills. Basically, the ridegline that runs between Pleasanton/Dublin and Castro Valley/Hayward.
Palomares Road has a quite substantial three mile climb, with the first two miles pretty stiff (I think I had a cold...and I did a long, fast-ish ride the day before, so wasn't fresh). WESTOVER WINERY is near the top of the hill. Low key, pleasant, somewhat elegant and rustic winery. Nice people. I wanted to try wine from grapes grown up on the ridgeline, so he poured me a very crisp 2009 Chardonnay that I liked, although it was not typically Chardonnay-ish. He said that he wants to get a little more roundness in future vintages to show more chardonnay character. The 2003 Livermore Valley Cabernet was pleasantly muky and mature, with good fruit and a lot of earthy character. I would buy this.
On Sunday, after foolishly bicycling through San Francisco on a crazy traffic day (Folsom Street Fair), I stopped at Donkey and Goat, who were pouring their new releases. I enjoyed the meaty, dark, and herbal Carrignane. The 2011 Pinot was outstanding, with blazing acidity (not too much, just great) and delicious dark cherry fruit and earthyness. The Syrah from Mendocino was also delicious, with true Syrah meaty-plum skin character. But the real surprise of the tasting was a Chardonnay from sonoma??? on ungrafted Wente Clone grapes called "Untended" because the vineyard was discovered in a semi-ruined state. This was a revelation wine for me, with layers of complex flavors I cannot even describe.
I enjoy Donkey and Goat quite a bit!