We have just returned from a wonderful trip to Napoli and the Costa D'Amalfitana. We stayed 5 nights in Sorrento. We rented a car (my husband is good with driving small roads) because we thought, after reading all the information in Rick's book as well as other guidebooks and websites, the best way to get around (we aren't usually tour people).
However, even now, in the "shoulder" season, it was too crowded at any of the big towns (Positano, Amalfi, Ravello) to park anywhere. You would have to park SEVERAL kilometers away and on the very dangerous narrow road.
However, our hotel (Sorrento Flats - highly recommend) recommended we take the ferries. There are several daily ferries from Sorrento to both Amalfi and Positano (you have to take the bus from Amalfi to Ravello) as well as organized tours.
The regular ferries are about EUR20 a ride between the towns, and you could even do both Amalfi and Positano (but not Ravello too) on the same day if you wanted.
The tours are discounted this time of year as well, and add things like a visit to the Emerald Grotto (a bit overrated and possibly close like the Blue Grotto if the seas are rough) but also a good choice for only a little more than the cost of a ferry ride.
I was a bit surprised that none of this information about the ferries and tours were in any of the books - not Rick's, not Rough Guides, not Lonely Planet, when these are very convenient, easy and not expensive (more than the buses but a lot easier than the ride, unless you are not good on boats; they are big enough that usually is not an issue).
And maybe these are better this time of year - we were told that the entire coast and Capri were 'very quiet' compared to how it is in July & August and earlier in September, when it is virtually impossible to get around anywhere.
But for anyone going to Costa D' Amalfitana, I suggest looking into the ferry schedules for getting around.
Finally - we were going to take Mondo Tour to Capri, but warning: if the seas are rough it may not go because the boat is small. We signed up for a different tour because of this - through Tours & More (find on Trip Advisor) which was less expensive (EUR 65, also discounted for time of year) the only difference is no snacks, and a bigger boat that can get around much better, also with the optional Blue Grotto experience (also if open).
Hope this is helpful to everyone going to Costa D'Amalfitana and maybe some info about the ferries can be added to the next guidebook version?
Enjoy your travels!