Marty worries that bringing his phone overseas will cause him to rack up thousands in cell phone bills. Should he just keep his phone on airplane mode? Leo says no, that turns off everything. Marty can go into his data settings and turn off data roaming, though. Then he can just rely on local Wi-Fi hotspots and download Google Maps and cache them. That way he can still use maps for travel.
What about texting overseas? Verizon is the worst for international travel, but he can call them and set up an international data plan for texting and limited data. He should check out this page at verizonwireless.com for more information. (Thanks to Scooter X).
Marty could also just get a local SIM for local data, but he'll have a local number. That may not be a big deal, though. Marty should check out prepaidwithdata.wikia.com for the countries he's traveling to and what services are offered.