I'm not in the field yet but it isn't an issue in our class. We started out with 7 females and are down to 3. But our large group of guys don't manage to treat us any differently. The a-holes are a-holes, doesn't matter what side you fit in on.
I'm far from a feminist. I am secure enough in my gender and intelligent enough to know that realistically the
average female doesn't have the strength to do what the average male can. However, I expect a chance for the non-average female that
can. If you think you can, then by all means, go out and do it. If she can, then she should have the right to work that job. But I also support equal testing of both genders. You want to go out and be treated like a man, then you should be graded like a man would as well.
I don't feel as if I have to "prove" myself in anything I do just because of my gender or sexuality. Respect, trust and camaraderie are built over time and through experiences. What is meant to come will come from real trials and tests of my skill and ability. Not any overzealous attempts to prove that I can play with the big boys too.
As far as my sexuality is concerned, I'm very open about it. I am a bisexual female in a monogamous marriage to a male. But I do not shy away if people ask about my sexual orientation. It has never really been an issue for me other then people assuming that because I'm bi and married I am also polyamorous. But that is just something that comes with preconceived notions and ignorance. I can deal with that.. and you have too if you are going to be open and out. The only time it has really ever been a big problem for me was when another student heard of my orientation and made it a point to act as if I was hitting on/flirting with every single female student in the class.

(but that guy is the definition of douche bag)
So, so far, in interactions with my extremely diverse class, instructors and evaluators, I've never felt as if EMS would be hostile to my particular demographic. Granted, as I said, I'm not in the field yet but I'm feeling fairly comfortable about what to expect.
If it ever does become an issue, it's just that more satisfying when you prove them wrong. ^_^