route by car from cetona to sorrento

Valerie - you can find driving directions and times between any two points in Europe at viamichelin.com

If 'best' is fastest, mapping software probably over-estimates the time. Use the freeway. With a full tank and an empty bladder, you'll be well past Naples by the three hour mark (figure eighty mph just to keep in the flow of traffic most of the way). That last tweny miles out the peninsula can take either a half hour or a life time.