San Ysidro, Calif.
The rosy glow of a Pacific sunset signals the end of the day in the San Diego metropolitan area. But here, high above the city and ocean, the San Ysidro hills come to life at dusk.
Where the hills dip to the Mexican border, several hundred Mexicans milled about on a recent evening. Eyeing US Border Patrol agents to the north and the setting sun to the west, they waited for darkness to cloak their scurry across the border.
An island of rugged terrain dividing the urban seas of Tijuana and San Diego, the hills and maze-like canyons of San Ysidro are striped with the well-worn footpaths of Mexicans traveling north into the United States. Hundreds of Mexicans - 1,000 on a recent evening - are apprehended every night by the Border Patrol here in the most heavily trafficked sector of the 2,000-mile US-Mexican border.
From the vantage of these hills the political and economic controversy over the ''flood of illegal aliens'' takes on very tangible dimensions.
The nightly lineup at the border appears to be a testament to year-end statistics showing record numbers of aliens caught during the holiday season - traditionally the slowest period in the migration cycle.
There were 20 percent more recorded apprehensions in the San Diego area during the last three months of 1982 over the same period in 1981, reports Dale Musegades, deputy chief of the Chula Vista Border Patrol sector (which includes the whole San Diego area). December is traditionally the slowest month of the year, with roughly one-third of the number caught during peak months. But during December 1982, nearly 20,000 apprehensions were made - much more than half the 33,500 peak in March.
While December had the year's lowest number of captures, its relative position ''. . . more than likely represents a real increase in apprehensions,'' says Dr. Wayne Cornelius, director of the Center of US-Mexican Studies at the University of California, San Diego.
Critics of the Border Patrol say these statistics aren't a fair gauge of the number of aliens crossing the border because of multiple apprehensions of individuals and the absence of crosschecks on each apprehension. But Dr. Cornelius says the numbers provide a ''rough proxy'' of the intensity of pressure to cross the border.