Alberto is a very friendly, easygoing host who also happens to be a tour guide, so he knows everything about Palermo! Gave us awesome food recommendations.
The airbnb is a hostel/b&b type of apartment with multiple rooms. We never met any of the other guests though. It's clean, in the very heart of the historic center, the volunteers were kind and helpful. Only downside: the street can be rowdy on weekend nights with clubs and bars blasting music till after midnight - bring ear plugs!
Apart from that, highly recommendable! We had an awesome time.