Joel Barnard is enthusiastic. "I was real impressed," he says of President Reagan's speech Thursday night. "It made me want to send him a telegram to tell him how much I support him. There are going to be a lot of critics of these cuts. But it's like they say, 'Everybody wants to go to heaven, but nobody wants to die.' "

You might not expect to hear such praise for Reagan's economic program from Joel Barnard, co-owner of the San Marcos Real Estate Co. in this pleasant town of 24,000 about midway between San Antonio and Austin.

His company has suffered through its worst summer in years. High interest rates have dried up the mortgage market, and at noon today the office was filled with agents who had nothing better to do than talk about hard times.

But when the conversation turned from real estate to Reaganomics, the mood in the room changed dramatically.

"I supported this kind of thing a long time ago, before Reagan came into office," says Sherryl McPherson. "I knew we couldn't continue to live in this dream world. I'm willing to give him more time."

These are the voices of Reagan's Main Street, the "heroes" he described in his inaugural address in January as "a special-interest group too long neglected . . . made up of men and women who raise our food, patrol our streets, man our mines and factories, teach our children, keep our homes and heal us when we're sick."

They are the counterpoint to the bears of Wall Street who, the president says he believes, have given up on his program before it takes full effect.

This city gave Lyndon B. Johnson his college degree in 1930, and 50 years later it gave Jimmy Carter a 100-vote victory. But today, the people say they support Reagan. If San Marcos is indicative of other small towns in America, Main Street hasn't given up on Reagan's economics.

People here don't agree with every detail of the president's economic program. Many think the Defense Department could stand deeper cuts than Reagan wants. They don't want basic Social Security benefits tampered with. And there are some warning signs on the horizon. But right now they say they want Reagan to continue on the path he's chosen.

"I think it's good that he's sticking to his guns," says Margie McClanahan, who works at the Kroll-Marney Pharmacy on the town square. "I back him all the way."

On the other side of the square is Byron Wallace, a visitor from Dallas. "He's tearing 'em up," he says of Reagan. "Everything he's doing I like. We need a little conservatism in this country." He pauses. "But he ought to cut the defense budget a little more."

The feeling seems to be the same almost everywhere in town. Inside Lamar LaCaze's barber shop, half a dozen men are chewing over the program a little after 9 a.m.

"I just hope the country has enough patience to see if it works," says Roger Guthrie, who works at LBJ's alma mater, Southwest Texas State University. "We're all paying for overspending since World War II."

At the university a few blocks away, a group of women in the student aid office are also discussing the speech, and all but one say they support the Reagan program.

"I hope he'll get us out of what we're in," says Beverly Elliott. "I don't think he's the one who did it. It started long ago." Does she believe Reaganomics will work? "You've got to have faith in something," she says.

But one man who's lost faith is James Natal, a custodian at Lamar Middle School on the west side of town, and in his story is a note of caution for the president. Last November he voted for Reagan, but since then he's lost a part-time job because of the budget cuts and he now believes Reagan's "gotten out of hand."

"I don't believe in it," he says of Reaganomics.

Right now, Natal is in the minority, but as more budget cuts take effect, others in San Marcos will feel the pain directly, and in another six months, Main Street could be less patient with the president if the economy hasn't turned around.

As city detective Mario Reyes put it today, "I'm not sure I'd give him as much time as he seems to want."