NEW : Mass media : More than 400,000 people attend the Mass . NEW : The Pope urges Mexican Catholics to remain true to their faith . Many onlookers wave balloons , flags and banners as the pope arrives . The pope travels to Mexico first .
NEW : State media : More than 400,000 people attend the Mass . NEW : The pope urges Mexican Catholics to remain true to their faith . Cheering onlookers wave balloons , flags and banners as the pope arrives . The pope travels to Cuba Monday .