Not sure about Mexico, but our experience with Roam Mobility here in the US has been horrible. They pair with T-mobility, I was hoping for reasonable data speeds and phone coverage, transiting the US from Detroit to California I had high speed data only once or twice and I lost phone coverage a few times even though we are rarely off the interstates. Even our cheapie TracFone (thank you Mr. Slim!)was much better for phone coverage. I would find out who they are pairing with (and if you get the same access as the folks who are directly with that company) before trying them.