We loved staying at Mariza's and Diogo's place. The flat is right in the heart of Alfama, close to tram 28 and the museum of fado and many fado restaurants.
The house was just as described, clean and well equipped and Diogo was always very helpful throughout our stay including at check in and check out. The staircase is a little steep at first but once you get used to it it's quite easy to go up and down.
I would definitely recommend staying here.