If your lectures will be on the Science Site or on the hill, and you're looking for a social college community, I would definitely recommend St Mary's College. Mary's is right next to the Teaching and Learning Centre, right across the road from the Science Site (which also hosts the university library), and only a very short walk up the hill to the other hill colleges. It is such a social college, with its own (newly revamped) bar, weekly sport & society socials, and lots of formal dinners and balls which are brilliant. It's also catered, which really offers an extra social aspect as everyone sits together in the dining hall for meals; this was extra handy during freshers week when everyone was eager to break the ice and get to know each other. You don't have to worry about being put in a shared room either; all rooms in Mary's are single rooms, most of which have communal shower and toilet facilities which you would share with the rest of your corridor.