Cast my vote for having your own rental car.

The coast road is narrow but it's not that bad, and besides, you'll be able to tell some good stories when you get back about hairpin turns and Italian drivers. We were there many years ago in the summer and except for a few problems finding parking, we had a wonderful time. It's even a beautiful place to get stuck in traffic while waiting for one of those big buses to negotiate the turns.

Also, I want to second Janet's opinion of Ravello. We had a wonderful room with a balcony overlooking the bay. The hotel's restaurant was on a covered outside patio high above the water and every night there were fireworks from the shore which burst at our level (far enough away, luckily). It was magical!

Have a great trip, Al Sonoma, CA, USA