I feel I must respond in favour of such groups. We have stayed many times in January at the Values. Yes, BTGs are annoying because of their size. They disrupt the food courts and clog the bus lines, but by and large these are nice kids. They smile and are pleasant to us, even hugging us for small courtesies and remembering us the following year.
I remember being there at the same time the 15s from Argentina were there. I don't speak Portuguese (or Spanish for that matter), but I found those girls respectful and they tried to be helpful. We use a wheelchair, and they were always holding the door for us, and smiling. I remember getting on a bus to DTD. We were the only ones on the bus that were not part of the group. I'm by nature a friendly person, and don't mind chatting with people. The girls tried to converse with me too, which made for some confusion and a lot of grins. Some of them started singing loudly, and I must have shown my disapproval because someone yelled something in Portuguese and they stopped singing. We of course were the first on the bus, and the last ones off the bus. As we made our way into DTD, the girls parted for us to pass, and yelled to the girls ahead that we were behind them. They in turn yelled ahead to the others as they parted and made way for us. Now, they could have been saying in Portuguese "Watch out for the crazy lady with a wheelchair", but I don't think so.