It's difficult because even though all animals have some intelligence and way to communicate, they don't think in the same way people do. Gorillas are really closely related to people though so they share some a lot of the same concepts. It's still a lot of work to teach a language that both sides can understand, but it's easier than it is for other smart animals like crows or octopuses that have really different brains as well as the physical limits like not having hands.
I think it's more like... I can talk to them, the same way if a dog turned into a person it could try to talk, but I don't know if I'd be able to say anything very intelligent, and I wouldn't know what they were saying back. I can talk telepathically to people when I'm in morph though. Probably to animals too, but they wouldn't understand what I was saying.