It sounds like you're headed for a fun adventure! How exciting. When you're outside the US, you are not on the Verizon network, so there are roaming fees to use your phone. You can use WIFI at no extra cost, so if your phone also has WIFI calling capabilities that is something you could use as well.
We have temporary travel plans available here: http://vz.to/2nejEru.
If you decide to not add a Travel plan, I recommend keeping your phones in airplane mode to prevent accidental usage. WIFI will still work on most devices with Airplane mode on.
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