My colleague and I were in Barcelona for a conference, and stayed at Carlos and Reyes's place. We had a great time! They are very kind and accommodating hosts. The apartment is conveniently located in La Rambla, very close to several major tourist sites and good restaurants (Reyes wrote us a great list of recommendations for places to eat, so we could avoid tourist traps). We walked everywhere. The room is very small, but there is a good amount of storage space (and you should be out exploring Barcelona anyway!). Carlos and Reyes are also very generous with sharing their living space, so the small room doesn't matter. I highly recommend staying at Carlos and Reyes's place.