Carlos's place is in the perfect location! My partner and I stayed here for 3 days, and we did not use public transport (apart from getting to and from the apartment from the train station) at all! It is close to all the sights you want to see, as well as many restaurants.
Communication was excellent! We were arriving into Rome very late at night, and Carlo stayed up to make sure we were let into the apartment safely. He was understanding.
Would definitely recommend!