Things are a little tougher for foreigners walking across the border into Mexico

Walking into Mexico at the nation's busiest border crossing with the United States is no longer an uninterrupted stroll for foreigners.

Pedestrians going to Tijuana from San Diego at the San Ysidro crossing must choose between a line for Mexicans who get walk through unchecked, and a line for foreigners who must show a passport, fill out a form and — if staying more than a week — pay 322 pesos, or roughly $20, for a six-month permit.

Travelers have long followed similar protocol at Mexican airports, but the new border procedure marks a big change at land crossings that . . .