Yes, by both sexes. The most hilarious incident came as a result of my sudden determination to do something different one saturday so I resolved to see a play. There were two theater companies operating in the city, one a fairly traditional sort of thing and second that was wildly liberal tackling revisions of plays, difficult social commentary, and even the occasional full nude play (A Midsummer Night's Dream for example was performed entirely in the nude which made a strange story even more odd).
The play I went to see was Angels in America. I didn't know it at the time, but the plot of the play revolves around how different individuals deal with being gay. It was also held in a place entitled OUTstanding. The seemingly arbitrary capitalization didn't strike me immediately as being meaningful. I watched the play and was relatively unimpressed overall but before I left I started talking to a gentleman about my age. He was very pleasant but eventually he started making subtle passes at me. When I finally picked up on it I politely declined his offer. When asked why, I simply and very reasonably noted that I was not gay. This news came as a terrible shock to him.
Somewhat put off by the fact that he was shocked I wasn't gay, I gave the matter some thought and realized he had a decent point. I did go and watch a play about gay people struggling with being gay. This play was held in the building of an organization that supports gay rights and so forth. It was also located on the same stretch of road as the two notable gay drinking establishments. Considering how intensely homophobic the city in question is, the fact that I would choose to do such a thing by itself might imply I was gay.
Then I realized that my garb, chosen randomly from my closet that morning, was actually hilariously flamboyant and my girlfriend, originally scheduled to accompany me to the play, was held up at work.
Thus, I went to see a play about gay people being performed in an institution that aggressively promotes gay rights on the gay block of town all while dressed flamboyantly and not accompanied by my girlfriend. I suppose I understand why it could be assumed I was gay.