I have been reading that you should avoid WDW when Brazillian tour groups come. Does anybody know when that is? Are they there in early July?
There were lots there mid July. I wouldn’t say you should avoid going though - they are easy to avoid because they are so slow moving. My mum was only reminiscing at weekend what fun it was to ride Soarin with a large group of them.
I believe that most of the tour groups come during school vacations: December/January (end of school year) and then again June/July into August.
I will say I have been in the world at the end of June with many tour groups and I much prefer them to the HS groups in the world in April. In April many NE HSs go on spring break and take trips to the world. Most times those 16 and 17 year olds are unsupervised. They behave like 16 and 17 year olds with no one around to watch them. The Brazilian Tour Groups are usually supervised. Although they are large groups and loud I have found they usually have an adult with them.
Regardless, other than the ToT line you can usually escape both groups 
We were in DW mid July last year and stayed at Pop Century and it was overrun with Brazilian tour groups amongst others. I am avoiding them this year and going in August.