People in Sicily are passionate and friendly. Really friendly! They can invite you on a café, at home and they might be very touchy because of their character and warmness. Sicily is not very big and there aren't huge distances, so it is easy to find a spot for hitchhiking.There are 3 highways in Sicily, along the northern coast from Messina to Palermo, along half of eastern coast from Messina to Catania and crossing the island in the middle from Catania to Palermo. Waiting time as always depends on lots of factors such as your spot, attitude, panel etc, can be from 5 minutes upto several hours if you don't understand you have to change place. Hitch-hiking in Sicily might be hard, but it is more than possible and rewarding. It usually works well on small national roads, but, as usual, it is not easy to hitch out from a bigger city.
It is possible to hitchhike onto the island (it means you don't need to buy a ferry ticket), if you hitchhike somewhere before Villa San Giovanni (Artti was 200km away) with a sign Sicily. The tickets for the ferry are paid by vehicles, that means it doesn't change anything 1 or 5 people inside the car (exactly as for the british channel tunnel); so that also standing at the harbour or asking people it's a very easy option to get inside a car and enter for free. In any case don't worry, also on foot, the ferry is free..lots of locals just walk on it every day without any ticket and in case you really want to buy a ticket, it should cost from 1 to 2.40 euro...
It is possible to take buses without a ticket and have long rides out of the city.
Other Useful Info
Traffic in Sicily is crazy.
Hitching in Sicily can be pretty slow. It took Ecasalicchio 24 hours to do about 150km one time. There aren't many service stations on the central autostrada. It's easy to find yourself having to hitch illegally on the autostrada; though is definitely better to avoid it. Entrances roundabouts and national roads are so much better options, also because lots of people prefer avoid taking motorways.