We stayed 6 nights at Carlos' place. The area is quiet and within easy walking distance of the old part of Bilbao and the Axturi tram terminus (stops include Abando (tourist info), the Guggenheim, and the San Mames bus station). Carlos welcomed us for our late evening arrival with cider and walnuts and showed us around the apartment. It's clean and comfortable with everything you need. He had collected various information leaflets for us and also advised us to buy a Barik card - €3 for the card to which you then just add credit. This is an absolute boon for discounted travel on the city's transport networks (including the airport bus). Recommended.