We stayed with Alfonso for a week to explore Madrid. Overall, our stay was fantastic and I would definately recomend satying with him!
The flat is in a quiet neigbourhood, which is in walking distance from the center (~30 min). Alsonso was very welcoming and was not only a nice host, but a helping hand from the very beginning. Of course it is different for everyone, but we got along very well and spent some time together. As a plus, Alfonso is fluent in Spanish, German, French and English!