The area between the Mexican border, and the nearest checkpoint in the United States.
Its called that because this area is inhabited by Mexicans. (close to 85%) Since there are a lot of Mexicans, there are a lot of Mexican heritage in the area making some areas look and feel likeMexico, and also at times speak border language.(i.e Tex-Mex)
"Hey man where are we? There's a lot more Mexicans then white people."
"We past the checkpoint in Falfuras. We're now in Pre-Mexico"
Pre-Traumatic Stress Disorder. For a time-travelling resistance fighter, the stress disorder that results from dealing with traumatic events that technically have not happened...yet. But they damn sure will if you don't keep that robot from killing the girl. Or stop those robots from killing your son.
"I just had a nightmare about death machines dancing the macarena down a highway made of skulls."
"Hasn't happened yet, dude. Ever since you jumped outta the time machine you've had a serious case of Pre-TSD."