We will be taking a ferry from Capri to Naples in Sept (15th) and picking up a rental car at the train station. Here are my questions.
We want to leave Capri around 9:30A.M. - which ferry is fastest? easiest? Which ferry port in Naples is easiest access to the train station? How easy is it to get on the highway toward Rome from the train station?

Why are you renting from the train station rather than the airport? You can get the airport bus from Piazza Municipio quite close to the main ferry terminal, and you would be starting further out of town. I certainly wouldn't chose to drive in Naples! Suggest reading the ferry timetables online - I don't have the links anymore, but your guidebook should have them.

Hi jane - Molo Beverello dock has easiest access to Naples station (- Piazza Garibaldi).

There are several companies running hydrofoil services between Capri-Naples - e.g SNAV, NLG, Neapolis.

Here's the current timetable link (- times vary throughout the season):

http://www.capri.net/en/ship-timetable

If you are driving straight to Rome, why not rent in Sorrento rather than from central Naples?

Steve

I took the SNAV hydrafoil round trip, I believe there is some form of ferry leaving/going to Capri at least hourly if not before. The highway to Rome is not far at all, and if you feel lost stop and ask directions, the Italians really quite friendly and most speak good English.

Why do you want to rent a car at the railway station when there are frequent, fast trains to Roma and beyond?