I just graduated from a DO school and had interactions with other med students from other schools.
A story:
we had a girl in my class who was very aggressive with her sexual orientation for the first couple of weeks. Her anger at everything really was uncomfortable, because frankly the rest of us didn't care what her lifestyle was. Once she stopped being angry all the time she was a really great person and that's all we all cared about. There were apparently other folks in class who were bisexual, swingers, homosexual, etc. No one cared. We were all too busy studying and trying to help each other through med school. Gathering with family/friends? They brought their partners. No big deal. Moms and dads brought their kids. No big deal. Unless the partner/spouse/kids were total jerks or PITAs. Then we just didn't like the partner/spouse/kids/etc.
so, take home messages from my experience in med school:
1. no one cares what your sexual orientation is unless you try and make it their business.
2. They care if you're a good person
3. They care if you will be a good team player and help your classmates as you will expect them to help you.
4. If you try and alienate folks you can definitely succeed. But really, we're all too busy to care about your personal life just as you'll be too busy to care about ours.
5. If you make it a big deal, it can definitely become a big deal. If you treat it like others treat their boyfriend/girlfriend/partner/husband/wife/etc., no one will think twice. Really.
Now before you flame me for being a bigot or prejudiced or anything else, I fully understand there are folks who have had difficult experiences. I do. Try being told you're too old. Or being disabled. Not much you can do about those, and difficult to hide. I guess my point is avoid the places that are flat out nasty (but don't rely on just one source and don't rely on whether there is an "advocacy group" or not - get the skinny by going there, talking to a bunch of students... there aren't any "advocacy groups" for the disabled or older students or for parents at any school I know of either and yet those students seem to do just fine) and find a place you can be happy. Of course, if being happy means you have to have a bunch of clubs, marches, parties, exclusive gatherings, etc. for any one particular cause, I can't help you. We were all too darn busy studying to do any of that unless it was the "pass bacT study club" or "dirty mnemonics you will definitely remember club".
And for the record, I know students with same-sex partners (I'm unclear as to the politically correct term here, so please pardon me as I really try not to offend anyone) who are perfectly happy at Touro-Ca and NYCOM for exactly the reasons I listed above. They don't hide it, but they also don't make it a big deal.