I dunno, I think I might actually just be oblivious to it. I've definitely found myself being stared at a couple times, so I smile back, but then they avert their eyes to quickly for me to gauge the situation. I think another part of it is I come off as straight. When my roommate (a woman) and I used to go out, strangers would say "How long have you guys been together?" And I'd be like "Umm... I'm gay."
We used to joke that I should get a t-shirt that said "I'm not with her." and another one that said "Heauxmeauxsexual" (its an LSU thing. Spelled the "cajun" way, but pronounced "homosexual") cause apparently I was a bit of a cock-block for her.