It depends on which course really. Girton is not far from the west cambridge site which means that it's close to compscis, vets, physics, some other science courses. It is pretty far from the city center, probably 20+ minute bike ride. Wolfson is about 10 minutes, and it is probably second furthest (followed by Clare Hall, Churchill, Fitz, Robinson, New Hall). But it all depends on your course and what you like. From what I've heard the college is very large and campus-y more like York and those sorts of places.