I gotta be honest with you: when I was a child, we were never particularly crazy about the "Festino of Santa Rosalia", (or in Sicilian Fistinu), our Patron Saint of Palermo festivity. In my family, it was definetely labeled as a popular and too crowded event to be part of. Nevertheless as I grow up I decided to join the feast and I really enjoyed it. I do confirm it's the most popular and super-crowded of the festivity in town, but probably for this reason is also unique and extremely evocative.
There are a couple of things that are typical during the Festino night: first is the so-called "babbaluci" (basically escargot) that Sicilians cook with oil of olive, a couple of cloves of garlic and lots of parsley. I have never had the courage to try them, but some people really love them.
The other very traditional thing is called in Sicilian "u scacciu", which is essentially made of calia (roasted chickpeas) and semenza (pumpkin seeds), plus sometimes other nuts like pistaches or peanuts.
The typical "Palermitan" buys a portion of those nuts that are placed in a "coppo", a brown sheet of paper, with the shape of a cone.
The idea behind the scacciu is that people always need to have something to eat while either watching the Procession or waiting for the fireworks at the end of the night.
I know it may sound strange, but we cannot stop eating, even if they are small little things.
When I went to my last festino with some friends, a couple of years ago, I met a group of Americans that were both shocked and fascinated by that incredible mayhem across the "cassaro", the heart of the old city.
I think is a great experience for tourists to be able to partecipate to such an incredible feast, because as I said earlier, yes it's crowded and noisy, but it also reveals the real soul of Palermo.