I sat next to someone on the airplane who was a photographer by hobby, and he said that he liked to take photos that "you cannot retake another time" and as he explained that concept to me, I realized he was talking about his interest in "street photography." Something that makes me feel shy, suddenly. But with the warmer weather finally here, I set out with my camera after dinner and saw this image in a basement bar as I walked by. As I stopped to quickly snap a photo, he looked up and had a nice smile . .. and said it would be fine to post the photo.
Great shot! Most people don't mind. Smile, be friendly and have a short explanation prepared in case anyone asks. Carry a couple of business cards so you can show them you aren't about to do anything strange with their picture and ready to share them if they're interested.