Stayed in Maria's apartment for 4 nights and found it great as a base for exploring the city. The apartment is small but it is very clean, and is perfect if you just need a place to sleep and shower before heading out for the day.
We found it got hot at night, but that using the fan made it comfortable enough to sleep. You can also open the balcony doors at night as the restaurants in the street below pack up at around 11pm.
Transport links were very good, it's less than 10 mins walk from the metro station that goes directly to the airport. Transport links to places like the beach, and the impressive science/ arts complex are also a short walk away and very easy to use. The apartment is right in the middle of the touristy part of the city, with many landmarks literally a 2 minute walk from the front door, and plenty of restaurants and cafes outside your front door as well.
A great place to stay for a short break if you don't want to hang around inside all day.