it would depend on whether their visa granted them worker eligibility status
I would warn them that Admiral Ackbar said, "its a trap!"
I would tell them that earth is a wasteland,there is nothing to see here,that they were mistaken,then I would ask them to take me with them if its not much trouble.
what kind of aliens are we talking about? Xenomorphs? Necromorphs? Vulcans? Ewoks? the little squishy ones from Pizza Planet? or just people from another country?