The paved road that whipsaws through steep mountain passes turns to dirt and rock about two hours' bus ride south of here. With every passing vehicle, dust billows through the cracked windows, covering everything and everyone. But there is little southbound traffic and the bus arrives on schedule.
Coalcoman de Matamoros, in the southwestern part of the state of Michoacan, is a small, remote farming and ranch town with plenty of cowboys but few paved streets. This is the time of year when Coalcoman does its biggest export business: sending people to work in the United States, many of them illegally.
For now, the town plaza with its well-trimmed gardens is still fairly crowded in the evenings, as men and women gather around talking, laughing, and passing the time. Trucks, cars, mules, horses, and burros mingle as they pass by.
But each day more people from this town, mostly men, head north for work in California, Texas, and some other states. Some have valid US entry documents; some have fake ones; and some have nothing but determination.
Sending laborers to the US has become a ''tradition'' in Coalcoman that dates back decades, says a young resident who has gone to the US to work illegally several times.
Since the late 1800s, Mexican towns like Coalcoman have been sending workers to the US to earn much more than they could at home. Their US employers have been eager for their cheap labor.
Most of the Mexicans from Coalcoman return during the winter.
As a number of American scholars have noted, this flow back and forth from Mexico generally receives little attention in the US when the economy is prospering. Yet because US unemployment rates have risen lately, so has criticism of these workers.
But while high unemployment sends political signals flashing across the US, in Mexican towns like this, a tradition of exporting labor is unlikely to change soon.
Almost everyone here has a relative who has gone to the US, legally or not, to work.
So many people from Coalcoman have done so that, within a few hours of arriving here, this reporter:
* Met a young man who had worked in the US illegally for a number of years and, as is typical, has a valid California driver's license. He introduced a friend who is also planning to go - illegally.
* Talked to Jose D., a farmhand, who, while riding a trotting burro, explained to this reporter, who trotted along beside him on foot, that it takes him up to 15 days to reach California sometimes because he often has to wait several days at the border to cross with the help of a ''coyote.'' (Coyotes are smugglers who charge a fee to take people across the border.)
* Spoke with a student who had crossed the border illegally to work and now is thinking of going back - to study.
So many people leave each year that the area suffers, says Miguel Sanchez-Castaneda, a local farmer.
Standing near a cornfield on the edge of town, he points up to the tree-covered hills where only a few cornfields break the green with their patches of white. More fields could be cultivated, he says, if more people stayed year-round.
But in an interview on the patio of his modest but comfortable home on an unpaved side street, he explains that the reason farmers leave is that they lack the money to farm. So they go to the US, earn much more than they can here, and send money home. Frequently they later rent their farmland, and buy a house and a lot in town, says Mr. Sanchez-Castaneda.
On one edge of town, there are many brick homes built in the past several years with earnings from the US.
Mr. Sanchez-Castaneda sets an example of how earnings from the US can be used: two homes and 16 cows, enough, he says, to provide a retirement income from the sale of milk. He also owns six acres of irrigated cornfields and 63 acres of pasture.
Mr. Sanchez-Castaneda has US immigration documents that he proudly displays. But a Mexican study shows that undocumented workers in the US also send back money to their families.
This money provides what some analysts call grass-roots foreign aid to Mexico.
But one former undocumented Mexican worker found he could earn as much here as in Los Angeles. Now he stays here year-round and runs an auto repair shop.
Some analysts contend that the best way of curbing the flow of undocumented workers to the US is for Mexico to increase opportunities for Mexicans to earn more. Some critics of Mexican efforts say too much attention is being paid to urban development and not enough to rural development.
But there are some signs of new government attention to Coalcoman: a new government office building, a new plaza, a market under construction - and the jolting road north is being paved.