As an American, I can say that when approaching Americans (even ones you have nothing in common with), personal questions (and compliments) are OK, as long as they are not rude. They can actually be really good "ice breakers" (getting rid of initial awkward silences). If they are personal but not rude, most Americans will either answer (feeling more friendly from the start), or just say something like ("that's a little too personal"), but that is fairly rare. This is all in a casual situation, not a business situation. Just smile and keep good eye contact. If conversation doesn't naturally follow, it probably never will. :)