How would they communicate with us? Telepathy? We shouldn’t assume they’d have that ability. In the movies, every alien civilization speaks English, but let’s get real. And I don’t buy the “universal translator” thing either, unless it is programmed based on intimate knowledge of a given race – which would be difficult if not impossible for the aliens to acquire of humans, if they are different enough to begin with, which is perhaps likelier than them being similar.
So if they can’t communicate with us – which seems likely – then there is no way of knowing their intentions except by watching them act, and vice versa; and even then we may be confused. So it’s not like we could just say, “Sure, go settle down there.” If we pointed or tried to shake their tentacle, they might think we are threatening them.
Even if we could communicate well enough to establish peace, the people of earth would never agree as a whole what to do with them, and it would only take one person doing something stupid to ruin everything.