As President Reagan's fiscal revolution begins its trickle-down path from Washington to the states and cities, it's time to introduce Juan Patlan, a man ready to meet the challenge.

For the past decade, Patlan has lived off the federal government as president of the Mexican American Unity Council, a federally funded community development organization.

The experience has given him some unexpected insights into the role of the federal government, and today Patlan sounds as if he sprang from the pages of George Gilder's "Wealth and Poverty," the book that is required reading in the Reagan administration for its philosphical argument in favor of supply-side economics.

"I used to be the biggest proponent of government giving poor people everything," he said in his spacious office on the west side of town. "Now I think that's tremendously wrong. You don't develop any discipline. If you get everything free, you lose your resovle and you're not as productive as you would be."

Patlan grew up as the son of a migrant farmworker in south Texas, graduated from a segregated school system, bummed around for a few years, got a degree from the University of Texas and finally settled in San Antonio in 1967, where he went to work for the Mexican American Unity Council, one of many groups formed as part of the Great Society's war on poverty.

"We're grateful for the war on poverty experience," Patlan said. "If it weren't for that experience, I'd still be saying the government ought to give everbody everything for free."

About 90 percent of Patlan's $3 million to $4 million budget comes from Washington, but he is not worried that Reagan's budget cuts will slow down his organization.

"Our position is that we are going to survive. No, not just survive, but thrive. And that's bescause we run good programs," he said. "Our feeling is that there's going to be money around to fund some programs, but instead of 20, there may be just three or four, and they will be the best programs. We feel we're among the best."

What about the other 16 or 17 who get shut out? "There's been so much money available, it made it easy for people to apply," he said. "As to the soundness of the idea or the ability of a group to deliver, nobody asked."

Patlan is pleased with MAUC's record. The organization bought an abandoned elementary school from the city a few years ago, poured hundreds of thousands of dollars into it and created modern office space in the heart of the Mexican American community. A branch of the public library leases space in the building, among other tenants.

"No one came to us and said, 'We've got $1 million to do the old Crockett Elementary School, why don't you apply?'" Patlan said. "We did it."

MAUC is involved in a several economic development projects in San Antonio, including a 10 percent share of the new Hyatt hotel now under construction and a venture capital gorup funded in part by local banks. "It took us tow years to get that money," Patlan said proudly.

Now Patlan is committed to economic development as the route of advancement for minorities. "I don't want you to give me anything," he said. "Just put me where the opportunity is. . . .

"There are truly needy people who need help, but what happened in our country is the line got blurred, there was so much money available," Patlan added. "The danger with Reagan is that he'll go overboard in the other direction."