I studied many years ago (back in 2001 I think) at Saena Iulia in Siena for a couple of weeks. I just checked their website and it looks like most of the same people work there. Mauro is still the director. He was very helpful. I also studied at another school in Siena during a different summer, but preferred Saena Lingua. Of course the other school may have changed by now as it was back in 2000.
I have also taken classes (private) with Andrea Quarantotto through Bolognalingua in Bologna in 2011. After spending time taking classes, both in Hawaii and in Italy, my lessons with Andrea worked out perfectly for me as they were tailored to my individual needs and I did not need to spend time trying to understand foreign Italian accents from the other students in my class. Of course I have forgotten so much of what I learned now! I really enjoyed my week studying with him.
I would recommend both depending on what you are looking for. Loved both locations. Of course both of my studies were not very recent so things may have changed.
If you do decide to inquire with either, please let them know Susan from Hawaii says hello. I no longer live in Hawaii but they will know me (if they still remember me) from there.