How do we know they're refugees? Mexico isn't thaaaat bad.
They're not coming from Mexico. At least, the majority aren't. They travel through Mexico, sure, but most originate in Honduras, Guatemala, etc. Central American countries.
Edit: From the US State Department's
travel advisory:
The Department of State continues to warn U.S. citizens that the level of crime and violence in Honduras remains critically high. This Travel Warning supersedes the Travel Warning dated December 24, 2013, and includes additional information on crime and security in Honduras, as well as updated contact information.
Tens of thousands of U.S. citizens visit Honduras each year for study, tourism, business, and volunteer work without incident. However, crime and violence are serious problems throughout the country, and the Government of Honduras lacks the resources to address these issues. Since 2010, Honduras has had the highest murder rate in the world. The Honduran Ministry of Security recorded a homicide rate of 75.6 per 100,000 people in 2013, while the National Violence Observatory, an academic research institution based out of Honduras’ National Public University, reports that the 2013 murder rate was 79 murders per 100,000 people.