Armando Avila inches his car forward in the long line of vehicles crossing from Juarez to El Paso. At the border station he pulls out his Mexican passport and shows his US visa.
Mr. Avila works and lives in Juarez, but he often crosses to El Paso for its restaurants, shops, and movies. Tourists and businessmen -- both Mexican and American -- keep the boundary bridges busy.
A much smaller flow of Mexicans enters the US illegally between the checkpoints to work, shop, or visit family.
''We (Juarez and El Paso) share a lot of the same problems and opportunities, '' says Mr. Avila as we pull onto a highway heading for downtown El Paso.
Problems . . . and opportunities. That is probably as good a way as any to summarize the ties between the border cities -- and between the Mexican and American public.
For while the flow of illegal immigrants to the US from Mexico is viewed in some quarters as a problem and in others as an economic necessity for both nations, other ties are widely seen as opportunities.
Trade and tourism are two such ties of opportunity.
Tourism has its ups and downs (Mexico worries that this is one of those ''down'' times), but trade has been steadily increasing.
Mexico sends two-thirds of its exports to the US, including oil, natural gas, tomatoes, silver, shoes, and fruit. In turn, Mexico buys about two-thirds of its imports from the US, such as automobile parts, corn, airplanes, industrial equipment.
The other side of the trade equation is much smaller, but significant. US exports to Mexico between 1977 and 1980 nearly tripled -- to some $15 billion -- according to the US Department of Commerce.
Mexico is the No. 3 trading partner with the US after Japan and Canada. And there is a growing amount of US investment in its southern neighbor.
''US investors feel politically and socially safe here,'' says Eric W. Gustafson, Mexican vice-president of one of the nation's largest private conglomerates, located in Monterrey, Mexico.
But trade is not the only thing improving between the US and Mexico, he says. ''Understanding in general is higher than before.''
Mr. Gustafson went to summer camp in Dallas as a child. He remembers that people then still had the impression Mexico was a land of just dirt roads and donkeys. The televising of the 1968 Olympics in Mexico City presented millions of Americans with a different view of Mexico, he says. Last year's summit meeting of developed and developing nations in Cancun, Mexico, and publicity about Mexico's new oil wealth have further heightened awareness of Mexico in the US, he explains.
Another bonding agent between Mexico and the US is the personal warmth expressed to Americans when they visit Mexico.
This reporter encountered such warmth repeatedly on a recent three-week trip through Mexico. I was welcomed almost as a family member for a stay with a Mexican family in Mexico City. Even in the small, central Mexico town of Coalcoman, where my purpose was to write about a very delicate part of the lives of many local Mexicans (their illegal trips to the US as workers), the people were genuine in their welcome and fairly open.
(I must admit feeling a little conspicuous sitting in a corner chair in the one-room, long-distance telephone office of Coalcoman loudly -- because of the connection - dictating a story to this newspaper detailing illegal crossings into the US by some of the local residents. Even if no one understood my English , by the time I left the town dozens of residents knew my purpose there and were still friendly and helpful.)
In the evenings in the small central plaza of Coalcoman, young Mexican men who had gone to the US -- some of them illegally -- told of another tie that affects the US and Mexico: the strong tie Mexicans feel to their own country. They talked of missing their family and friends while in the US and how they never quite fit into American life.
In his book ''The Labyrinth of Solitude,'' Mexican author Octavio Paz writes about the settled Mexicans he encountered on a long stay in Los Angeles. Such a Mexican, he wrote, ''does not want to return to his Mexican origin -- neither does he appear to want to join the North American way of life.''
It is this suspension between two worlds that is one of the hardest things for Mexicans who come to the US. And it may be the reason why so many return to Mexico regularly. Several times this reporter was told by Mexicans who said they had legal permission to go to the US that they preferred to stay in Mexico.
Others who went, legally or illegally, told of missing the close Mexican family ties, the custom of taking time to keep friendships alive (and not on a ''shelf,'' as one Mexican put it), the generally slower pace of life.