Pretty sure the Network Extenders are not considered "global ready" devices like a Jetpack or a USB modem would be. Is there a reason why you purchased a Verizon device instead of a local Mexican carrier device for this location? Any phones that you have would have their own roaming packages and if you have landline access to run a Network Extender to a home, then WiFi is likely going to be better for your mobile devices anyways.
A network extender creates a small Verizon cellular network based on the incoming internet connection. However Verizon may not have legal clearance to broadcast in the spectrum for that foreign country. Some other carrier may own that airspace which would be a legal issue VZW would want to avoid.