It‘s a pretty apartment and well equipped for a couple. Since there is just one room more people would mean some lack of privacy.
We would strongly suggest adding an air-con. Since it is the rooftop apartment the heat is pretty hefty. Especially when using the cool staircase it feels like walking into a wall of heat. Being in a lively neighborhood it is rather not advisable to leave the windows open if one wants to get some sleep. If you don‘t mind temperature and some noise in the night it is the perfect place near to the center and the trendy quarters of Valencia. We had a good time there, Matthias