When big Don Lovett opened the door of his bus yesterday - a Southeastern Stages coach from Georgia - 46 square dancers and square-dance callers poured out onto the Lafayette Park grass.

Bob Bennett of Valdosta, Ga., founder of the Jekyll Island Jambores and a premier Georgia called ("Have mike, will hike," it says on his card), got out his tape machine and turned up the music. Everyday danced.

They were waiting to go across the street to the White House for a tour, and this group never stands still when it can dance. "We dance at all the rest stops," said Bob Bennett. "Outside the restaurants, next to the gas pumps."

Almost everybody was dressed in white and peach. The women wore peach dresses with full skirts and petticoats. Men wore peach shirts and white vests; some wore white shirts and peach vests. Don Lovett, who was driving the group to the 26th National Square Dance Convention this weekend in Atlantic City, watched every step the dancers tok.

Lovett said he began square dancing two years ago - "Blondes have a way of makin' you do things," he said - and that he's still learning and these are the best people he knows to learn from. "That's why I pulled this job," he said.

There was Rod Blaylock of Albany, Ga., a tall man with slicked-back hair drinking a can of Mr. Pibb soda he had brought with him. Rod Blaylock taught Jimmy and Rosalynn Carter how to square dance. There was Bennett, known for his square dance music on Thunderbird Records (He did "Load the Wagon" on the Longhorn label). There were Mac and Virginia McDonald of Macon, presidents of the Georgia State Square Dance Assn. They've been to 13 straight Jekyll Island Jamborees.

The night before, this busload and two other busloads of Georgians had danced at the Pentagon. Why the Pentagon? "Just wanted to," Bennett explained. "You can go to any church hall every day. You can't go to the Pentagon every day."

They said they like it around here. They'd come to the inauguration. "We like to froze to death, and got lost a dozen times, but we made it," one said. But Don Lovett complained about the hotel prices; they were "too high," and his mattress too thin. "I'm a big feller," he said, "and everytime I rolled over my hand would go over the side and hit the floor. And $4 for breakfast. Awful."

Rod Blaylock said, "When I'm riding around here, to me this is a northern place. Yeah, it's up the road, definitely up the road, at least for me." Blaylock, when he's not around home in Albany, puts in time in Dawson, near Plains. He taught the Carters to square dance in Dawson.

"He was a state senator, living right there in Plains, and he just walked into an open house and said, 'My name's Jimmy Carter and this is my wife, Rosalynn. I want to learn to square dance.' I was just the instructor for the class. He was just one of six squares, or 30 couples. He signed up, paid his dues, graduated, and received his diploma.

"I gave him 18 lessons. He learned 50 movements. He was always grinning, smiling, having lots of fun. About the sixth lesson, I called out 'corner.' That means you go over to the girl on your left. He says, 'I been over there and I haven't felt anything that feels like a corner.'

"He danced at the club level two, three years. And he joined the 'Merilegs.' That's a word taken from American Legion. That's where they danced, at the American Legion hall."

Blaylock and the others did not get to see the most famous square dancer of all yesterday during their White House tour. But that failed to dim Blaylock's enthusiasm. He called square dancing "the biggest participatory adult recreation in America today." Even if his estimate is only close, it would seem Jimmy Carter is in step with much of America.

"It's a real good clean sport," said Don Lovett. "You don't drink while you square dance and you don't square dance while you drink."

"There's never been anybody that's come with alcohol on his breath, never," declared Virginia McDonald. Come where? She was asked. "Anywhere," she said. Mrs. McDonald, who once sewed a dress for Amy and selected Rosalynn's dress for a Jekyll Island dance, added, "And there's never been a joke too shady to tell a grandmother or a 2-year-old child."

With that, Mac McDonald cried, "All aboard. All aboard." Lovett closed the bus door and brrrrmmm, brrrrmmm, maneuvered onto Pennsylvania Avenue, headed out of town.