We had a great time at Luis's place! Everything was as described. The apartment is comfortable and cosy with a big living room. The street is indeed quiet, but also very close to the Metro and at walking distance of the Palacio Real and lots of restaurants and bars. Luis couldn't be there himself, but he made sure someone was waiting for us when we arrived, and he texted us to make sure everything was ok.
Would definitely recommend for a citytrip!