First time in Spain, first time in Barcelona. Rosa's apartment is pretty centrally located, making it easy to get around the city. In general, I walked everywhere I went, but sometimes took a cab when I wanted to save time.
The area is pretty quiet, but there are tons of great restaurants within a short walking distance (there is an entire avenue of nice restaurants right up the street). There is a laundrymat right around the corner with good, fast, efficient machines and it is open until 2200. There are plenty of little grocery stores and other shops and pharmacies nearby.
The apartment itself is a bit old, but in a quaint, charming way. The internet is good, the AC works great. The bathroom is pretty small, but it works. The bed is not large... queen at max. It worked for the 2 of us, but if you are particularly tall or love to roll around and sprawl on the bed... it probably won't work.
Rosa was a great host, very responsive and accommodating. Highly recommend this apartment.