I know everyone disagrees when they go off to college, but the fact of the matter is that most of the friends you have now (from elementary and high school) you won't have, or won't be as close with, by the time you're done college; whether you live at home or not.
If they go to college, too, they'll have less time to keep the friendship, and/or change a lot to the point where it's not the same as it was. If they don't go to college, they'll be the same lame-ass bum they've always been. You're going to college; whether you want to or not, you will change. A lot.
Of course, there are some exceptions, but basically what I'm saying is don't cater your life to your current friends. You're still young, you won't talk to most of them 5 years from now. Don't jeapordize your own future for them. I don't talk to most of my old friends; half of them still don't have their high school diplomas and they're 22 FFS! I, along with everyone I'm in college with (same program or not) have changed immensely in the last 4 years. You will too, and you will come to value different things in relationships and friendships.
Besides, you don't live that far from home - Don't go home every weekend, but go home sometimes if you want. Get your friends (and girlfriend) to visit you, too. If they aren't willing to do that, then what kind of friends are they, anyways?
I'd say stay in the dorms (maybe find some cheaper ones, though. I thought my school was ripping us off...) for at least your first year. You'll make a lot of new friends, and have a metric shit-tonne of fun. My first year in residence was probably the best year of my life.
By the by; if none of this makes sense it's because I, like Jak, am a little sauced right now. MMmm... Hoegaarden....