Our family had a wonderful stay in Juan Carlo's apartment (children 7&9). The location can not be beat. A very should walk to the Plaza Alfalfa, with restaurants and grocery store (Super Sol). A couple of things to note:
1) there was construction in the adjacent building. Work started at 8am. So if you are interested in sleeping in - this will not be possible (Work happened from Mon-Friday). We have children..so sleeping in isn't an option anyway.
2) there was no "binder/book" of places to see, recommended places to eat, etc. We really missed this. Exploring Seville was fun, but would have been handy to have a few "local tips."
3) the mattress in the main bedroom could use an upgrade. It wasn't the most comfortable.
The apartment was very clean, and the kids loved the toys / books that were available in the 2nd bedroom.