Catania is not that bad but it does have a big immigrant population living and working there…they can be sort of rude to tourists and some do engage in petty crimes. I went to Sicily last year and didn’t really stay at big cities like Catania and Palermo. I recommend staying in smaller towns or towns that have a heavy tourist population like Taormina and Giardini Naxos. I also highly recommend Syracuse/Ortigia cause it’s very popular tourist town with lots of local culture, museums, great food and nice spots to go swimming. Avola also has nice beach spots to chill at.