Authors:

Otherwise you have to repeat a lot when you're filming. And I've seen the film and it's in a border town in Mexico close to the border with the United States, so of course you have a lot of traffic and noise and dogs barking right nearby, and for that you have to repeat a lot and Robert Rodriguez didn't do that. Smart, smart, smart, you better have smarts also.

Source: collider.com
Otherwise you have to repeat a lot when you're filming. And I've seen the film and it's in a border town in Mexico close to the border with the United States, so of course you have a lot of traffic and noise and dogs