Sergio's apartment was not hard to find. Sergio was waiting for us when we arrived. The apartment is located on the 4th floor. My cousin and I are backpackers so it was easy for us to get up there but it was still a workout, I can imagine how people with rolling luggage could have more issues.
The apartment was very nice, as in the pictures. Since we went in December, it was cold but Sergio had a gas heater that we used when we were in the apartment (turn off at night though). Wifi works well in the living room (activate it at the kitchen table, then you can move around in the living room no problem and even up to the bedroom).
The only thing I didn't like too much was the duration of the hot water. Sergio had warned us that he had electric heating for the water so my cousin and I showered one at night and the other in the morning to be sure that one doesn't get cold water, but even then, hot water lasted only 5 minutes. I have long, thick hair so no way I could of washed my hair in such a short time. It was also very cold when we went so you felt more the need to take a hot shower, I'm sure in summer it's not so bad.
We used the kitchen on our second night. It is small but has everything that you needed.
Location was great. We bought groceries and snacks at a little store 1 minutes from the place. During the day, we walked everywhere and had no issues finding our way back.
Sergio was great! I wrote to him by email a few times during our stay and he replied very fast. We planned to go for drinks with Sergio the second night but we didn't feel well and had to cancel. He also called a cab for us for 5am on the 3rd day since we needed to be at the airport for 7am.