Rita and Carl have an awesome apartment in an amazing location! While it is extremely close to the metro, we mostly walked everywhere (restaurants, shops, museums, parks, etc.). There's a cute coffee shop and an ice cream/pastry shop right on their block which were both very good and convenient. Also, El Rastro flea market is right at the end of their block and is a must if you want to do some inexpensive shopping!
The flat was perfect for two people, and had everything we needed for our stay. I communicated with Carl the few days we were there, and he was extremely helpful! Our flight was a bit delayed, but he arranged a pickup for the keys and allowed us to check in early AND out late. Can't really ask for more!
As some other reviewers have mentioned, the building elevator is currently under construction so you will need to bring your luggage up three flights of stairs. Wasn't a problem for us though! And others have mentioned a smell from the construction, but we kept the balcony doors open the entire time and didn't notice it whatsoever in the apartment.
Would highly recommend and would certainly stay there again.