Was in holiday in Palermo in May. Stunning place as is much of Sicily.
If I may share a couple of tips that may be of use to someone.
Have a look at staying in Mondello. Its outside Palermo on beach 20 min bus drive away, which is fairly reliable and very regular. It tends to be a bit cheaper than Palermo and being on water is a bit cooler than the city.
The other tip is dont get a car if you can avoid it. You wont need it in Palermo and it will shed your nerves if you have one, in terms of driving with the nincampoops and loons and trying to find a parking place. You also stand a good chance of being ripped off by rental car places who will try and put every scratch (which you are likely to get) down to you.
Obviously if you want to drive around Sicily that may be different and a car may be necessary but just to stay in Palermo dont get one.
Palermo was stunning and I found nicer than Catania which with the exception of views of Etna was not that nice.
The food in Palermo is amazing. Treat yourself to Pasta alla Norma. Incredders. Enjoy.