We had a wonderful stay at Maria's. The apartment is truly sun-soaked any time of day :) We did not spend much time in the apartment, and went to the city center for much of the trip. It was clean, spacious, cozy and welcoming. We loved the plants, views, and balcony! Maria is kind and helpful with recommendations on anything from restaurants to transport, and helped us have a convenient check in & check out.
The 758 comes by here and got us to and from Barrio Alto many times. City transport was generally a bit erratic, so we took a couple taxis to save time (only about 8E to the airport, 10E into town). The subway seemed more timely, so consider this option too. Frankie Hot Dog was halfway between the airport and AirBnB - definitely recommend this option for your post-travel meal!
Overall, we had a delightful stay. I would absolutely book again.