Traffic in the U.S. enters Mexico at the San Ysidro border crossing, the world's busiest, in between San Diego and Tijuana.
Less than 20 miles separate downtown San Diego from Tijuana, but at times, that distance can seem much greater. San Diego's new mayor, Bob Filner, has embraced the relationship -- and he plans to open an office in Tijuana to help strengthen the bond between the cities. Reporter: Katie Orr
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