MEXICO CITY—American tourist Michael Anderson expressed amazement Monday at the vast number of Mexicans populating Mexico City. "I guess it's obvious that the city would have a lot of Mexicans, but I wasn't mentally prepared for it," Anderson said. "I mean, really—they were everywhere. Tons of them. On every street corner. They were just everywhere." Last year, Anderson experienced similar culture-shock at the number of Asians in San Francisco's Chinatown.