Palermo, Sicily

We are going in September and staying in Castellemare di Golfo, about 35 minutes west of the Palermo airport. Yes renting a car for that portion of our trip.

Welcome to the forum.

Try the search function, you'll get lots of hits.

It depends on what you want to see.

It appears you have only 5 nights. In such short time if you want to see only Palermo and Monreale (on the hill above Palermo) and maybe Cefalù, then you don't need a car (actually you don't want one while in Palermo, one of the most congested cities in Europe). If you want to be on the beach just stay in the district of Mondello (30 min from the city center by bus). Cefalù is just about 1 hr away by train. This alone will probably keep you busy for your short stay.

If you are not interested in Palermo, or you've been there before, you might want to venture out to visit Western Sicily, such as:
Segesta, Scopello and the Zingaro Natural Reserve, Castellammare, Segesta temple, Selinunte, Erice, Trapani, San Vito Lo Capo.
In this latter case, a car would be useful, since those locations are not necessarily well served by public transportation. My preferred bases would be Scopello or Castellammare.

For rental car needs I use www.autoeurope.com (a broker). They work with the major rental companies in Italy, like Europcar, Hertz, Avis-Budget, and Sicily-By-Car, a well established Italian rental company which is big in Sicily (where the company started over 60 years ago).