To add to what Eurostar said, I've also shown in my own solo story that Chance, for one, has been forced to deal with his lack of legal status in the world. In that story Dr. Q has provided a false passport and identity for him under the name of Paul Garrett, a British sales representative of Better Foods, Inc (the company that Pete won in a card game which funds the MBL... at least until now [mwah hwah haa] ).

It wouldn't make sense to me that neither Kit or Dr. Q would have taken all possible problems with travel into consideration and come up with solutions to them before sending the team off to a foreign country. They certainly wouldn't have waited for the day that they had to leave in order to get off their asses and do something about it. As well, the team has left the island in the past (Uruguay), and Dr. Q undoubtedly had made provisions for them then as well.