Tijuana, Mexico — The corn smell of roasting tortillas and the dancing light cast from a burning tire give the twilight a festive feel here on the ''soccer field,'' the unofficial port of entry for thousands of undocumented immigrants.
The ground is hard packed and spangled with bottle caps tamped into the ground by the migrating wave from the south that pauses here every night, without exception, on the route north.
As hundreds each day pause here for the curtain of darkness to conceal their illegal crossing into the United States, the good-natured Spanish banter of a border subculture comes to life.
Silhouettes clearly visible against sand-colored canyon walls, the immigrants talk with a serape-clad Mexican man and his wife who daily wheel their portable barbecue out onto the field, selling tacos and beer. Children from Colonia Libertad, a third-world jumble of a neighborhood that ends abruptly at the soccer field, sell used coats - $1 apiece - to migrants who arrive shivering without them. Polleros, guides who take groups of pollos (immigrants) through the canyons into San Diego County, are quietly gathering their groups together and setting prices - $100 a head for Mexicans and as much as $600 for Central Americans.
Here on this flat space just north of the point at which the nebulous international border is said to cross, the immigrants even exchange friendly conversation with the adversary, members of the undermanned uniformed US Border Patrol charged with keeping the illegals out.
Suspended momentarily along the border, the flow of illegal immigration takes on a human dimension before it fans out into the United States to become the faceless national problem that is the subject of great political and economic debate.
Ramon Robledo, shivering through his embroidered cowboy shirt in the early evening chill, shares his story with a stranger. From the state of Guerrero, south of Mexico City, Mr. Robledo estimates some 200 men in all have left his village.
''The only people who live there anymore are women and children,'' he says. He says he couldn't make enough money at home. His plan is to pick citrus near Santa Ana, Calif., and send all but $15 a day of his earnings back to his parents and his young family of four children.
''It doesn't make sense to spend the money here. They'll use it to buy pigs and animals to feed and then sell,'' he says.
Mr. Robledo won't bring his family to the US, he says, because it's ''hard enough to go myself.''
Asked if he isn't afraid of being caught in the US, Robledo, a father of four , chuckles softly, ''Fear is not having beans on the table.''
A dozen others draw near to listen and throw in their own observations. And whether it's the quiet, illiterate peasant from the central highlands of Mexico ready to cross the rugged canyons in a pair of plastic shoes, or the more sophisticated urban youth with a high school education and a penchant for gold chains, the theme is the same. While there is hardly a legal welcome mat thrown out for them at the border, they are certain there are US employers waiting to hire them.
Like many men in their hometowns, they've left their families behind and headed by bus to the border with nothing but the clothes on their backs. Their own estimates are that they will make 10 or even 100 times more money in the US than they could in Mexico.
From this border vantage two perspectives are clear:
First, it is easy to visualize the unbridled violation of US immigration law here. With the sheer numbers migrating north and this open space being only a fraction of the 2,000-mile frontier, it is ludicrous to think that US immigration authorities alone could effectively control the border. Indeed, at the legal port of entry in San Ysidro, Calif., just a mile from the soccer field , US Customs official Robert Rich says that he's powerless to do anything with those immigrants who try to enter illegally right under his nose. Of 35,000 immigrants caught with fraudulent immigration papers at this port of entry in fiscal year 1984, the US authorities prosecuted only five, he says.
Second, this border scene evokes an instant compassion for a wave of humanity that, except for the circumstances of its entry, is not that much different from the immigrant ancestors of nearly every American. Illegal crossings are about as routine for some as walking to work every morning. But here on the soccer field immigrants must cross into dark canyons and run, duck for cover in the dirt or prickly brush, and cross muddy streams. They hide from Border Patrol agents or, worse, from the notorious ''bandits'' who prey on the vulnerable immigrants. The motivation for such a humiliating trek begs for examination.
Estimates of the illegal immigrant population in the US range from 1 million to 6 million. Though illegal immigrants from Central American, Asian, Caribbean, and Middle Eastern nations are significant shares of the total, Mexicans constitute the majority, Immigration and Naturalization Service officials say. And Mexicans would be the most affected by the kinds of immigration reform US leaders are trying to produce.
''The question is how you can best deter illegal immigrants and continue our heritage of an open immigration policy,'' says INS Commissioner Alan Nelson. The tide of illegal immigrants, he suggests, ''is undercutting our whole our whole legal system. The American public could be saturated with so much illegal immigration that it would react by not letting anyone in at all.''
It is accepted by all sides that there is a large subculture of undocumented immigrants in the US. The main bone of contention in the debate over illegal immigration is whether the impact of this group is good or bad for the US. Some say the undocumented aliens depress wages, displace US workers, and tax the nation's resources. Others credit them with helping the economy by providing cheap labor for US business and agriculture not otherwise available.
The immigration debate promises to heat up as soon as Congress convenes next month. Mr. Nelson says the Reagan administration intends to pursue the same basic reforms that have been on the table for the past four years - sanctions against employers hiring undocumented workers, and amnesty for many illegal immigrants already here.
Sen. Alan K. Simpson (R) of Wyoming expects to reintroduce immediately some form of his portion of the controversial immigration reform bill he cosponsored with Congressman Romano L. Mazzoli (D) of Kentucky. Separate House and Senate versions of the bill were passed this year, but a conference committee failed to produce a compromise.
The Hispanic Congressional Caucus, often characterized as obstructionist regarding immigration reform, is planning a reform package of its own. ''There are no new ideas on immigration,'' says Susan Herrera, legislative director of the Hispanic Caucus. ''It's going to be what people will settle for'' out of an array of highly controversial solutions that have been on the table for several years.
How the problem is interpreted far to the northeast in Washington seems a remote, or even unknown, matter to the people congregating here daily on the soccer field and to many of the illegal immigrants already living in the US.
Ramon Robledo, who has been caught four times in a week by the Border Patrol, says he has never heard of the Simpson-Mazzoli bill. In fact, he is not even aware that he could apply to immigrate legally. He sums up his knowledge of immigration politics this way: ''I love Mexico, the government is the one that doesn't love me. The American government doesn't like me, either. But there's no work (in Mexico) and what I like is the work. It doesn't make sense to stay and make 400 or 500 pesos a day when in the strawberries or tomatoes (in California) I can make $70 on a very good day.''
Is there a law that could keep him out of the US? Robledo says he doubts it. Before he crosses the border and disappears into the shadows, he adds, ''If I don't make it today, then tomorrow, or the day after tomorrow.''