In June we rode our old tandem from Vacaville over Mt. George and into Napa, along Silverado Trail to Zindandel Lane, then to 29 and V. Sattui winery, where we stopped and had a delicious lunch.
http://vsattui.com Then we rode 29 to Zinfandel to Silverado Trail to 128 and on to Lake Hennessey and Lake Berryessa. There are some challenging hills around Pope and Chiles Valleys...if you hate hills you'll want to avoid these rides. Otherwise the scenery is gorgeous and the ride challenging. Google the various wineries and see what rides are available.
Have fun and enjoy!