Since I see them a lot here in San Francisco, I approach the ones I'm interested in and introduce myself, in just the same way I would approach anyone I would like to meet. I wouldn't introduce myself to an escort who wasn't alone. He could be with friends or a client. I walk up, extend my hand and say, "You're X, aren't you?" Since you're using his escort name, he automatically knows why you're saying hello. A simple introduction like that, to me, is not an invasion of privacy.