The Travellers House
The Travellers House is the best youth hostel I've ever stayed in! It is located centrally (3 minutes walk from the Plaza del Comercio), clean, nice, and with a generous and outgoing owners, for example, for New Years Eve they organized a beer-drinking contest to promote his "open bar" , a cooler full of beers that everyone could help themselves to. The decor of this place is fantastic and makes you forget the fact that you are having to share a room with 3 or 5 people in wooden bunks, and have a communal bathroom (which obviously is separated for boys and girls). I think they have a private room but I don't know what it costs or if it is hard to reserve and if it is usually always full.