The house is in the Santa Cruz area, great location midway between the Cathedral and the Spain Plaza, the two main tourist attractions. It can be slightly difficult to find at first because it is in a narrow closed street, but look for house 18, go inside the narrow street, and you will find house 20.
It is a quaint old house, and a nice way to see what it is like inside the houses in Santa Cruz, but it is darker than it appears on the photos and be prepared to deal with minor inconveniences that comes with staying at a traditional house instead of a modern building. This room was on the first floor, two other rooms were on the second floor and Juan Antonio lives on the third floor so plenty of privacy.