do the Yautja understand human language freely, without the use of an interpreter in their masks?
Short answer? No, I personally don't think so.
Yautja have their own language and have no reason to be taught earth languages unless they learn it on their own time, which I believe the average Yautja would not feel necessary. The Yautja visit earth for hunts and blooding rituals, and are specifically advised against general communication with humans.
However, due to the amount of time and resources they've invested into our planet, I do believe earth is very well documented. I also think their masks can easily act as an access point to a databank containing information about earth cultures, language, and other important things if they were to need it on the fly.
The only canon group of Yautja I would see being able to speak English and understand it without a mask would be the Lost Clan from Predators 2.
