Despite Mafia notoriety, Sicily is not a dangerous place and the biggest threat you face is not from the local capo but from the odd petty thief.
Modern-day Sicily is generally a very safe place to travel, and the likelihood of your vacation being affected by crime is low, especially if you follow a few common sense precautions.
In urban centres such as Palermo and Catania, you should exercise the same basic caution as you would in any large European or North American city. When walking through crowded markets or riding on buses at rush hour, be aware of your surroundings and don't flaunt your valuables or carry large amounts of cash in unsecured pockets. Pickpockets and bag-snatchers exist, as in any metropolitan setting, but your attitude should be one of prevention rather than of paranoia. Don't carelessly leave purses, cameras or phones lying about in street-side cafes, and don't keep valuables in plain view in a parked vehicle. If you're driving a rental car and feel unsure about the security of your neighbourhood, use an enclosed car park.
In the relatively unlikely event that you are a victim of petty theft or other crime, always report it to the police within 24 hours, and ask for a statement; otherwise, your travel insurance company is unlikely to pay out.
Sicilian traffic can be a daunting prospect, particularly in Palermo where the only rule seems to be survival of the fastest. However, outside the main urban areas, the situation calms down and the main concerns become curvy roads, potholes and iffy signposting. As a general rule, traffic is at its quietest around lunchtime, especially on Sunday, when few people are out and about.
Drivers are not keen to stop for pedestrians, even at pedestrian crossings. Sicilians simply step off the pavement and walk through the swerving traffic. In the major cities, roads that appear to be for one-way traffic often have special lanes for buses travelling in the opposite direction, so always look both ways before stepping out. On a positive note, pedestrian zones have expanded in recent years in the city centres of Palermo, Catania and other popular destinations.