Oh, brother! I just had my first experience with these groups! When we were there a couple weeks ago, we saw about 5 different groups and yes, some were from Brazil, one was from Paraguay, and one from Mexico so now I get what people have posted in the past about those tour groups.
All I can say is that they reminded me of how my nephew described his Marine boot camp experiences...those tour groups look just like a squadron of Marines on training missions. One day in Epoct, we encountered a group that was signing...okay, I don't understand Portuguese, but it was kinda like a Marine cadence.
Also, after reading all the comments about those Brazilian tour groups, honestly, I didn't think it was too bad. I mean, common sense tells me that if a large group and I are vying for the same doorway, either get in front of them or just wait till they are all done...less hassle for me. As for line cutting, I didn't see anymore than I would from a family...you know, one or two of the family members comes in a bit later...not an entire group of people though...very well behaved groups is what I saw.
But, oh...I could see a game of "Capture the Flag" with the tour groups...that would be funny!