I often wonder this as well, its rare for me to get male pronouns from strangers but I always wonder if they can tell and just kind of go with it anyways. I was at the baptism of two of my siblings a couple weeks ago, and this is a church I went to as a child but havent been involved in for a long time, so who knows me and who doesn't wasn't entirely clear, but I went in one of my new dresses and got complimented once on my dress and another time on my boots, and while it made me super happy, it was from younger looking girls and I couldn't keep from wondering if they were just trying to be nice to the very uncomfortable looking transgirl >_<. I try not to worry about because I don't think I have a right to complain, but the damned thoughts always keep up!
As a psych student I want to do an experiment where I measure pronouns used while I'm present and while I'm not (in reference to me) to gauge people being polite over genuinely accepting my identity.