That's according to a survey released today by the group Iraq and Afghanistan Veterans of America (IAVA).
Voters in Mexico will select a new president on Sunday, but the drug-related violence that has claimed thousands of lives in the last six years continues.
On Monday there was a shootout at the airport in Mexico City leaving three police officers dead. They were reportedly killed by other officers working for the drug cartels.
Felipe Calderon, who launched the war against the cartels when he was elected in 2006 cannot run for re-election because of term limits. The BBC’s Will Grant reports on the campaign to succeed him.