QUETZALTENANGO, Guatemala -- Across Central America, growing numbers of impoverished children appear to be setting out for the United States on their own, risking robbery, rape and death as they try to sneak illegally through Mexico and across the U.S. border. Last year, 6,460 underage illegal immigrants from Central America were detained in the United States while traveling without their parents and sent to government shelters, a 35 percent increase over the previous year. Many others likely slipped in undetected.