Hey. Monkeys can talk. They can learn sign language at a very young age; younger, in fact, than humans can. Does this mean that they're smarter? Or just more adaptable? Who knows? The point is, they can talk.
Communication is anything that gets an idea across. I could jump, hoot, and point. That would be communication. There's actually words and syntax with sign language. It is talking, albeit with your hands. No, I'm not pushing semantics. Lrn2linguistics.