Thanks, Good info on the train. Any guess how much a cab might cost? Any shuttle/limo services that we could reserve in advance?
http://www.romashuttle.com/
I've used them for city/airport transfers; you can book in advance online. Looks like the Civitavecchia-Rome shuttle is 130 euros for three people, which is more than the train (but less than what the cruise line charges), but it's door to door.