by Deborah Bonello Republican presumptive presidential nominee Sen. John McCain, who over the weekend went head to head with Democratic rival Barack Obama over the issue of immigration, heads down to Latin America today in a tour expected to include Mexico and Colombia. McCain is expected to focus on the issues of free trade and illegal immigration during his trip south. McCain is a strong supporter of NAFTA, the North American Free Trade Agreement, among the U.S., Canada and Mexico. But... ...