The best way to avoid falling asleep on the road in wine country? A little caffeine hit from the Napa Valley Coffee Roasting Company. They have two shops, one in Napa town (the south valley) and one in St. Helena (just south of Calistoga - the shop is on the west side of Route 29). The St. Helena shop is very comfortable and has artwork from local painters and photographers decorating the walls. All baked goods are brought in fresh daily and the baristas are pleasant (some are fun too!).
If you like the coffee at the Roasting Company, you can get it when you are back home wishing you were in Wine Country...just hit their website at www.napavalleycoffee.com.
I recommend the Organic Royal Select (even in decaf!).