I did something similar and it worked out well. Having searched through the threads in Wannabees it seemed that Naples Air Centre got the most consistent good press. They were very helpful with phone / e-mail queries and were professional and well organised when I was out there. Probably not the cheapest place, but I didn't want to risk getting out there and not getting everything done because the place failed to live up to promises - that would have been far more expensive.
So, bearing in mind that I've only got experience of the one school...
1) Radio is often busier but they don't worry too much about standard phraseology. In some ways easier because the controllers are really helpful, but circuit joins and unicom are a bit different so there are a few new things to learn. The first day I jotted down some favourite phrases and learnt them by heart, then I didn't have a problem.
2) Didn't think they bothered with NDBs out there any more. Lots more VORs, but not many of the NAC 152s have GPS. Navigation was practiced in much the same way as in the UK but in reality it is very different. Some of it is really, really boring landscape to fly over and sometimes you're pressed for ground features to identify where you are. In that way much more like proper ded. reckoning - you set course, fly it and find out how accurate it was as you near the landmark you're aiming at.
3) Think it's just the medical - you don't need a visa or anything, but probably best just to say you're there on holiday (which you are) and not elaborate further. As part of the familiarisation you've got to do some fairly easy flight tests and go through the main points of air law with an instructor. I'd say 1 week was a generous allowance.
As for the recommendation, I'd be happy to put NAC's name forward. Check in the Wannabees section - the topic comes up quite frequently.