I think that if you're a vegetarian for heath reasons vs. ethical reasons, you will have an easier time adapting to a relationship with an onmivore and vice versa. If you were concenred about the "ethical" side, there may be more conflict, because there won't be as much flexibility as far as your feeling when meat is in the house, animal rights, etc.
That sounds simplistic, but I think its a valid reality. A lot of what we can accept in relationships comes from having basic similar core values; if you value "meat is murder" and your partner feels that cows are here so that steaks may inhabit the Earth, then there will be a lot more problems than if you just feel that meat is an unnecessary choice.
I've always been a "casual" vegetarian, meaning I go through long periods where I don't eat meat. (I don't label myself that way - just the easiest way to quickly explain). When I met my partner, he ate meat, literally, seven days a week, and the only vegetables he ate were baby carrots and plain salad. My diet has remained pretty much the same through many years, and I'm pleased to say, without my coaxing, he now happily eats pretty much anything I make, including tofu and broccoli. It comes down to exactly what the wonderful posts above say: I don't push him, and he doesn't push me.
Now, I'm considering making a consious decision NOT to eat meat or similar any more, and I know that my partner will support me. I will support him if he feels he would like to continue to eat meat, which he's already expressed. I don't agree, but I have to agree. Besides, I know I have the upper hand because I'm the one that cooks dinner ;).
Every person has a right to decide what they will use to fuel their body. Every person deserves to decide what they feel is ethical, tasty, healthy, and right for THEM.
That being said, in any case: you will never change a person to be what you prefer, or what they aren't, or change what they deeply believe in - nor should you try. People do change - but rarely because someone else tried to change them.
If you can accept this, then you should have no problems. Some of your partners might still have issues, but believe me, vegetarianism will be the least of the wonderful topics that there will be to overcome, deal with, and stand by in the exciting world of college dating ;).