Yeah, there are hundreds of Americans and internationals, so you'll never be alone. It's nice and easy to integrate - just don't choose York House for accomodation, as that's where all the americans live. As for social life, Brighton beats everywhere else hands down, and loads of people are going to London all the time, it's about an hour away by train and perfect for day trips.
One thing, though, there's no such thing as "fall". It's called autumn!