You are so generous in your comments that I don't know what to say except thank you.
As far as photographing strangers, I do get told "no" quite often, and I'm getting used to it. But sometimes it works out. Like the lovely young woman in the last two pictures. I had asked someone else in the crowded streetcar for a picture, and they had said no. That's the point to look around, because everyone looks when you talk to a stranger. I think when people hear someone say 'no', then they have a second to think about it, and I can see by their face that they are ready to be asked.
I don't ask permission if it is from a distance, but for a close shot, I always ask. Maybe that's self protective. If they are close enough to grab me or my camera, I guess I better be careful!