MEXICO CITY – Mexicans living abroad sent home a record $23 billion last year, raising new questions about whether the government of President Felipe Calderón can afford to slow migration. In just one year, the amount of money migrants wired their families jumped 15 percent, according to Mexico's central bank, overtaking tourism to become the nation's second-biggest source of foreign income after oil. “This is a river of gold that flows into Latin America and Mexico. Daily. Weekly. Monthly. It never stops,” said Sergio Bendixen, president of Bendixen & Associates, a public opinion research firm in Coral Gables, Fla., that...