SILVER-TOOTHED and savvy about the ways of the United States Border Patrol, Jose Luis Pantoja slips through the dusty canyons along the US-Mexican frontier several times each month to find jobs in San Diego.For him, crossing the border illegally is like commuting to work. He can earn more in a day in San Diego than he might make in a week in Tijuana, where his wife and two children live. He even has career plans in el norte: To open a fruit stand in Escondido, north of San Diego. Mr. Pantoja symbolizes why America's 10-year illegal immigration crisis is far from over, despite passage of a landmark law five years ago designed to curb it. A number of experts predict the crisis will escalate, despite the 1986 law and President Bush's plan for a new free-trade agreement with Mexico. Population pressures south of the border are building so rapidly that growing numbers of young Mexican men will try to break into the US job market. "The 1990s are the peak decade for growth of the Mexican labor force," says David Simcox, executive director of the Center for Immigration Studies in Washington, D.C. "There are 1 million more Mexican job seekers every year," while Mexico's economy creates only 100,000 to 200,000 jobs a year. For the second year in a row, apprehensions of people trying to slip across the 1,900-mile US-Mexican border - considered a rough gauge of the level of illegal migration - are up. While the numbers are nowhere near the record year of 1986, when 1.62 million people were arrested, they nevertheless represent a upward trend after three years of decline immediately after passage of the Immigration Reform and Control Act of 1986. That law was designed to curb illegal immigration by penalizing employers who knowingly hire illegal aliens. In the fiscal year just ended, the Border Patrol apprehended 1.08 million people along the southern border - about 3 percent more than last year. Last year's numbers were 23 percent ahead of the year before. Here in the San Diego sector, the world's busiest illegal crossing point with half of all the arrests along the southern border, apprehensions were up 12 percent this year over 1990 (540,000 versus 473,000). While in the past, thousands of Mexicans crossed back and forth into the US to take short-term jobs, there is growing evidence that many now come to stay. One indicator: the number of women, often the wives of illegal workers here, who illegally cross the border is estimated to have nearly doubled since 1987. The number of children is up even more. Despite the increase in arrests, the US Immigration and Naturalization Service (INS) does not necessarily think the level of illegal immigration is rising. They attribute the increase in apprehensions to concentration of border patrol agents in heavily trafficked areas. They also contend agents are getting more efficient at catching illegals. The standard rule of thumb has always been that for every illegal immigrant caught, three slip through. In some areas, INS officials believe that ratio has been cut to 1 to 2. "We're getting better use out of personnel and resources," says Richard Kenney of the INS in Washington, D.C. Here in San Diego, where green-jacketed agents play an endless game of cat-and-mouse with aliens amid canyons of chaparral and Russian thistle, the Border Patrol says that it has been helped by a 10-foot-high fence erected along two miles of border here. The fence, which Mexican critics compare to the Berlin Wall, was constructed by the Border Patrol with the help of US Army welders, and was made of steel military landing mats ordinarily used to build temporary aircraft runways. It will eventually be extended another three miles to the Pacific Ocean. California National Guard, US Marines, and Navy Seabees have also helped by bulldozing roads through the brush to give the Border Patrol better access to the rugged region, which is sometimes made dangerous by border bandits who prey on immigrants. "There's been some opposition to the fence," concedes patrol spokesman Steve Kean, "but all concede it has reduced border crime and violence." Still, others believe the rate of illegal immigration continues at an alarming rate. Many blame Washington. "We've made about 5 percent of the progress we could because Congress and the Bush administration have dropped the ball on the question of phony documents," says Dan Stein, executive director of the Federation for American Immigration Reform. The 1986 immigration law requires US employers to check their new employees' papers for proof of residency, but a booming industry in forged papers has seriously undercut the law. Further, many employers still ignore the law, despite the risk of steep fines. As Pantoja reports, employers in California simply ignore the requirement when they hire him for day work in construction. Last month INS officials broke up what they believe was the nation's largest counterfeit-document operation. They raided a print shop here that may have supplied fake identities for as many as 1 million people. Researchers who study the border note that several forces remain in place that will continue a healthy flow of illegals northward, employer sanctions or not. They point to continued tough economic times in Mexico and a network of hundreds of thousands of illegals who have migrated here over the decades who can help others get settled. "The towns that have sent migrants to the US for the past 80 years are well organized to come here," says Sergio Zendejas, a visiting fellow at the Center for US-Mexican Studies at the University of California San Diego. "We don't have any indication that illegal immigration has slowed or that employers have stopped hiring illegal workers," says Kitty Calavita, a researcher in the social-ecology program at the University of California at Irvine. Still, some analysts believe, if illegal immigration hasn't stopped, it at least has slowed. Doris Meissner, former acting head of the INS who is now at the Carnegie Endowment for International Peace, notes that the 1986 immigration law was a compromise that reflected deep differences in the country about immigration policy. It wasn't expected to completely turn off the spigot. "If the number of apprehensions is holding at a million, I think we can live with that," she says. m not sure we could have expected anything more."