We stayed at Rosario's apartment for a long weekend and had a great time. The apartment itself is in a great location. It's walking distance to the old quarter, the beach, shops, and whatever you could desire. There's great food everywhere in the city as well.
The apartment was lovely with a beautiful balcony and very comfortable amenities and decorated very nicely! Rosario was an amazingly warm host and it was great getting to meet her. She was very friendly and welcoming as well as very patient with our weak Spanish skills.
We also happened to be in San Sebastian during Semana Grande which was a ton of fun with lots of concerts, fireworks, parades, and more constantly bustling around the city.