Didn't start using the mens' rooms until about 4 months on T. Was getting hostile looks in the womens' rooms for about... 1.5-2 years prior to that >.<
If people are directing you to mens' rooms, it might be time to take the hint. Or don't, like I did. Just don't be surprised when ladies start chewing you out for being in their bathroom.
You do bring up a good point about it possibly being dangerous if you're unpassable and go to the mens' room. Do you present as male at your college? You said 'college orientation,' so I presume you're a new student. Do you introduce yourself to new people with a male name? If so, it seems the mens' room would be the most logical option. If not, consider this: what will it be like to transition in the middle of your college education, asking friends, co-workers, fellow students, and professors who knew you years prior to switch to a male name and male pronouns? To have acquaintances who know you by your female name shout it to you in greeting, while you're working with classmates who know you only by your male name? That's my life right now... it's, uh, interesting. I'm still concerned about running into male acquaintances who don't know about me in the mens' room. Awkwardness shall ensue, I'm sure. I go to a small college and my department is smaller yet--everybody knows everybody, so this might not be an issue at a bigger school.
Anyways, the beginning of college is a great time to start with a clean slate, if you're comfortable with it. Only possible snag is if the university is forcing you to live in a female-only dorm for your first year. Or if your female name is on the class roster and the professor insists on taking roll (but that's easily fixed with an e-mail before class starts).