I live in northern Italy, so I don't have a lot of experience down south, but we took a short weekend trip down to Naples last weekend. (We passed Rome on the Autostrada)

They drive like idiots down there, I wouldn't want to ride my bike down there. Outside of Rome, and going north shouldn't be too bad.

Don't buy anything over here you don't need to. The exchange rate is terrible right now, and you'll pay 20% VAT.

I don't think there are any good GPS solutions for a bike, Garmin makes one, but I read a review online where the poster said it took a long time to calculate routes.