St. Edmunds is nice, it's a bit distant from the law faculty. They have some good parties and there seem to be a good mix of people, in comparison my college, wolfson, is mostly international and hughes seems filled with boaties and/or brits. You've already applied, so you'll get to come see it. I don't know anyone who's taking law but know several compscis, some vets, medics, etc.
Both Ed's and Wolfson are ridiculously laid back, especially if you're an undergrad. You'll have to be prepared to make your own way some times and make ridiculous conversation with PhD students about their subject, but that's the mature colleges. Of course they do have some pretty traditional bits because they are fairly old, just newly admitted into the university collegiate system. I'm going to be going to a formal there sometime soon, so I could probably say more after that.
Grad/Mature colleges get a bad rap here, but I honestly don't mind mine. However people from grad colleges tend to socialize separately and party less than regular undergrads, which sort of sucks (you people are so mean!) so you have to go out of your way to check out the other colleges and get people to go into town.