That's the problem, isn't it? How can we decode a theoretical alien transmission without transposing our own sense of meaning onto it?

It's like the X-Files episodes where they find the aliens are using encodings that were designed in modern history by humans. Binary (as if there is one standard binary), bar codes... These scenes are supposed to be huge revelations, but for any sort of programmer or engineer, they seem silly. Which wouldn't be so if they made a point about how the aliens are intentionally using our encoding systems, but that's not how it's presented.

Not hating on the X-Files though, that show is awesome.

If I were in charge of broadcasting a communication signal into space, I'd make it a very obviously square wave, or something else that doesn't usually occur on its own. So it really depends on if the signal was meant to be seen as a discovery mechanism.

Don't worry, it will most probably be limited to the USA. Aliens always land there.