God help me. We are praying," said John Karem, sitting in his open-air clothing and dry goods store a few blocks from the Mexican border.

At midafternoon, his small store is populated by one clerk and one customer, while only a few people pass on the sidewalk out front. A year ago, Karem said, "You would get dizzy looking at the traffic on this side of the street."

Karem is a victim of the troubled Mexican economy and its devalued peso. He said he once did about $3,000 worth of business daily at his store strategically located to capture street traffic crossing the border from Ciudad Juarez. Today, he said, sales total a few hundred dollars a day.

The situation is the same everywhere along the nearly 2,000-mile border between the United States and Mexico. Unemployment and illegal immigration are up, retail and wholesale trade are down and nerves are on edge. Devaluations of the peso have bankrupted small businesses, cost local governments millions in tax revenue and strained social services and law enforcement agencies.

Business owners and others along the border are increasingly pessimistic, recognizing that the drop in world oil prices and the size of Mexico's debt will probably lead to further devaluations and that a problem seen as temporary could linger indefinitely. That will inevitably lead to the collapse of more businesses in places such as El Paso.

Business recruiters here see a silver lining in this economic cloud: the lower the peso goes, the more attractive nearby Juarez will become for U.S. companies and the more the local economy will benefit. But that view is by no means universal. Instead, evidence mounts of ripple effects of Mexico's sagging economy.

A snapshot of the economic impact came recently from Texas Comptroller Bob Bullock, who reported that sales-tax revenues for January in El Paso were 47 percent below levels for January, 1982. The worst such case on the border was that of Laredo, whose sales-tax revenues fell 69 percent for the same period.

More than two dozen stores in downtown El Paso, including a large Safeway food store that catered almost exclusively to Juarez residents, have closed since the last major devaluation last summer. A Sheraton hotel shut down recently but was reopened last week under new management.

The downtown J.C. Penney's store once had one of the nation's highest sales volumes for its size. Now a few dozen customers in midafternoon are the norm. Even the flea market in south El Paso, a vacant lot once packed with stands and buyers, is suffering.

Conditions here are not unique. Statistics for the lower Rio Grande Valley, collected by Gov. Mark White's office, say that the Brownsville school district may collect just 50 percent of property taxes due this year because of business failures and that home sales are down 63 percent.

The data also indicate that housing prices have dropped as much as $20,000, that the number of persons seeking free medical care has increased 38 percent in the past year and that in one south Texas county applications for food stamps have risen almost 36 percent since August.

Mexico's economy has sent immigrants flooding across the border, putting additional pressure on U.S. Border Patrol agents.

"What we see is more and more people coming," said Alan E. Eliason, chief of the patrol's El Paso sector, second busiest in the United States.

The patrol's Chula Vista headquarters, the busiest crossing point, has been capturing 35,000 to 40,000 persons a month, and 100 additional officers have been assigned to the sector.

In El Paso, capture of those trying to enter illegally rose 60 percent in February, compared with February, 1982. The numbers are up 34 percent so far this month, a rate at which, by month's end, the Border Patrol may have apprehended 18,000 persons in the El Paso sector.

Illegal immigration has long been a fact of life here. Only the border-crossing rate has changed. But economic disruption in a community that was one of the most rapidly growing cities in the United States in the 1970s is something new.

Unemployment is officially 13 percent, but local economists say it is considerably higher.

"If you go out to the new mall, it's dead," a local resident said. "That mall was built and was booming while the peso was stable." He said his relatives once came from Mexico to El Paso and bought 20 shirts at a time but now buy "just one or two."

Some local doctors, who have relied on patients from the Mexican interior, reportedly have seen business drop sharply, while enrollment at one private school declined by one-fifth this year because devaluation made tuition too costly for some Juarez parents.

George Rodriguez Jr. is new director of the Texas Regional Development Center, which is attempting to boost the border economy, in part through tourism.

"I don't think it's a short-term problem," he said. "No one is predicting the peso will stay at current levels," meaning further devaluation is expected.

Many local businesses are equally pessimistic. A recent survey for the El Paso Chamber of Commerce found that almost one-fourth of local retailers say it will take at least two years to get back to normal, while nearly one-fifth said business would never return to previous levels.

"I think they have every right to be pessimistic," business consultant Thomas Lee said. "The south El Paso retail district has lived off the Mexican nationals."

Business leaders said the devaluation has made Juarez a more attractive location for U.S. businesses looking for low-wage foreign operations and that new industry there will help El Paso.

But a prominent El Paso lawyer said potential new industries are wary of the conditions in Mexico. "Any time the government of Mexico is unstable, it's not good," he said.

Sitting in his small store, John Karem knows little about prospects for business relocations in El Paso. He is just trying to hang on.

"I don't know how long we can survive," he said. "If it is two years before the peso is stabilized , this part of El Paso, it will be a town for ghosts."