Corrected entry: When the guy gets shot while relieving himself, if people a bit more than 10 metres away were shooting (and they were drunk) with the speed of a bullet, wouldn't it go a bit further than that?
Corrected entry: About 60 minutes into the movie, Jerry (Brad Pitt) has finished the task that has caused him to travel to Mexico and is able to return to the U.S. He gets to the airport and the airline attendant asks for his passport, he shows it to her but he realises that it's not his, someone had switched passports with him. He had to stay in Mexico, and thus the wackiness and mishaps continued. You do not need a passport to enter or leave Mexico, just a birth certificate.