This program was great for me, because I chose (and was accepted to) the immersion with Spaniard students option. If you can't get into this program, Salamanca might not be the place to go. API is great, but if you want to meet students from there, the best option is to take class with them. If you're looking for rewarding but tough academics, this is also your only option (although the spanish classes that API provides are great, because the teachers really know what they're doing and try to make class interesting).
API allows for a lot of travel, and even takes you many places which is a plus, we went to Paris for free as well as Barcelona. It was so exciting. And the directors and counselors we had contact with were so welcoming and understanding and always available for anything we needed. This was definitely the plus of the program.
Salamanca itself is a great, but small city. You can walk literally everywhere. So if you're a big-city person, you might like Madrid more, but I personally felt safer than ever in this city and no taxi fare ever!
In general, the problem isn't with API, its with the level of spanish you go with on this program. I would recommend it for high level spanish speakers who want to improve their 'Spain' spanish, and take classes seriously.