Using downloaded Google maps last year on the east coast of Sicily, my phone got us everywhere with precision, including a few places where the directions from the hotel proprietor were a bit of a driving puzzle.
A key is to make sure you've downloaded the maps for offline use - in advance while you're home on wifi. These are the steps I follow on my Android (Samsung) phone.
Download the Google Maps app from the Google Play Store.
Open the app and tap on the menu (3 horizontal bars in upper left)
Tap "Offline maps"
Tap "Select your own map"
Pinch and zoom the map out (to see a broad view of the continents) and then move over to Italy, then down to Sicily.
Zoom in on the area in Sicily where you'll be driving.
Tap "Download"
When the download is complete, notice that the maps says it "expires" on a certain date. You'll want to update the map again a few days before your trip so that you'll have a current (non-expired) map.
Open the Google Maps app and follow the steps above to get back to your "Offline maps"
Tap the 3 horizontal dots next to the map you wish to update.
Tap "Update"
Feel free to send me a message if your phone works a bit differently than above or you have troubles.