Generally used to mask the act of illegally downloading something.
Origin: Mexico is home to the small town of Juarez, which coincidentally is pronounced exactly the same way as "warez", which is another name for pirated software.
"Half-Life 2 just came out eh? Looks like I'll be going to Mexico tonight."
"My cousin in Mexico just lended me his copy of Doom 3 (it was a piece of shit)."