I have been to Naples before and will be heading out there on the 1st March (My return ticket to Florida with Virgin Atlantic was £196 + TAX)
What i did before and what i am doing this time is renting a car (
www.dollar.com) which cost approx 22US$ per day and the drive from Orlando takes about 5 hours during the day. This is by far the easiest way as the US bus and train network is not as extensive or easy as the UKs.
The acr pick up is in th airport and the drop off point is 10 mins walk from naples air center
PM me if you want any more advice
Spitty