(The Guardian) «The San Ysidro port of entry between Tijuana and San Diego is the busiest land border crossing in the world, with an average of 135,000 people passing through each day. The port is a vital connection between two growing cities that are separated by politics but inextricably linked by history, culture and economics.
People cross for a variety of reasons – work, family, travel or even medical treatment. For daily commuters the international border is just another traffic jam, albeit one that has grown in recent decades as the US has tightened security.
A side effect of increased inspection on the US side means wait times have extended dramatically over the years, and can be as long as five hours during peak periods. This means more potential customers, which has in turn seen more people working the line. This is apparent in the mix of vendors, who come from across Mexico, South America and beyond.»
Mexico Today USA 