I absolutely loved my time abroad in San Sebastián! My apartment (assigned by the program) had a beach view, delicious food was everywhere, and I learned so much about the Basque culture, which I never imagined happening before coming to Spain! If you join this program, be sure to sign up for a language partner. Not only did this help me improve my Spanish, but I now have a friend for life (I've been back to visit him twice since my program ended).
The best part about San Sebastián is that there is beauty everywhere you look. It's surrounded by lush greenery and there are plenty of outdoor activities such as hiking or surfing.
The USAC employees are also super helpful. I had no issue getting the classes I wanted, there were tons of recommendations for things to do in town, and I could tell that everyone there was really passionate about what they do.
I've been back to visit San Sebastián twice now and I can't imagine going to Europe without making a trip to my home away from home.