Near the sillicon valley, there are many wineries. You may visit the wineyard and can taste some of the best wines They would simply charge only USD20-25 in most of the places. Some of the wineries is located in the downtown of the San Jose but you may not feel the fresh air and the beautiful scenery of the wineyard.
Castle Winery in Napa Velley is one of the recent winery in Northern Califironia. The only difference of it compared to other winery is that it looks more like a castle. It is opened from 9:30 am to 5 or 6 pm. The address is 4045 North St. Helens Hwy Calisrogo CA 94515. If you had some time, I recommend you to visit.