Thank you for reaching out to us on our online Answers Forum. I can understand that you want to set the Slingbox up in Mexico and view it over in the USA. The answers to your question is: yes it would work. The Slingbox is designed to stream video from any cable box to your computer and mobile devices around the world.
Here are a few articles to get you started:
Hopefully these help.
The Sling Media Moderation Team.