Can't find a place on TA to write an official review so I am adding a forum post so it is searchable. We stayed a few miles outside the downtown Napa area and used a taxi service because we thought it was the safe and convenient thing to do. The taxis were always prompt and the drivers were extremely friendly and personable (compared to taxis in the northeast we were blown away!). They introduced themselves and provided us with their business cards so we could call them for a ride home at the end of the vening. While we were told we might have to wait ~20 minutes for pickup, they were usually there in about 5-10min. The vehicles were nice, clean and spacious. Their drivers go by number, so make sure you ask yours for their number if you want to request them at a later time. As for price - it was a very reasonable ~$12 w/tip each way for about a 10min drive.
I apologize in advance if this is inappropriate for the forums. Just thought this feedback may be helpful to some. Thanks to the frequent contributors for all their useful tips.