What decent restaurants are within walking distance of the hotel?
It is not in my walking distance but within a 5-10 minute drive.
I’m traveling alone and wondering if there is a social hour?
No, there isn't a social hour and the lobby area is small. If you are traveling alone I would not stay at this local because there is very little that would be walking distance. and you'd be walking along a main thoroughfare.
I'm not sure but call their direct Napa line @ (707) 226-1878 to find out.