I felt great the next day! But just to be sure I did the day of sightseeing in San Diego BEFORE the dentist visit instead of after. That seemed to work out well, and I was more relaxed than getting off the plane in a strange town and willy-nilly into the dentist's chair.
Speaking of relaxed, I highly recommend staying at the International Motor Inn, they take you right to the doctors door. I was a bit worried about border crossings and getting lost, and they totally took care of it all.