I studied in Salamanca for a semester, and it was wonderful. It's not tiny, but not as big as Madrid either. People really get to know one another. At a certain point, I knew where I had to go on a certain night to find someone I was looking for. It's a university town, so there are a lot of people there your age, and they're easy to find.
I studied wtih IES, you go through a university. There is also Don Quixote language center there that is great, from what I've heard.