Sitting on the junkyard wall across from the Harambee House Hotel yesterday, George Lyman, a truck driver, was picking out the celebrities.

"That's a CIA man," Lyman said, "and there's the police chief Jefferson..."

That's Jefferson? Where?" asked Lyman's friend Phil Swann, as he got a boost up the wall. "Man, who'd you say was coming? I ain't never seen all these kind of people on The Avenue before."

The celebrities were on Georgia Avenue yesterday for the local opening of Mayor Marion Barry's role as the city's international representative. Barry held the District's first state luncheon yesterday at the Haambee House for President Ahmed Sekou Toure of Guinea.

The luncheon drew an all-star cast that Barry described as a cross-section of Washington: Secretary of the Army Clifford Alexander; University of the District of Columbia President Lisle Carter; special assistant to the president Louis Martin; head of ACTION Sam Brown; D.C. Del. Walter Fauntroy and others.

Outside the hotel, a lunchtime crowd of hundreds, from the fast-food restaurants, the Banneker Recreation Center, gasoline stations, Howard University and the bus stops watched as long black limousines surrounded by policemen cruised up to the entrance.

Most of the onlookers seemed to know that all the fussing was over a visitor from Africa but no one knew whether it might be the president of Nigeria or the king of Swaziland.

A rhythm and blues band was on one side of the hotel entrance playing hit music and other side of the doorway was the U.S. honor guard and the 3rd U.S. Infantry's Old Guard Fife and Drum Corps. The corps was dressed in red and white Colonial Army outfits.

"They must have come to the wrong place," said one city official who asked not to be identified. "When they were around the only Africans coming over here were slaves."

When Toure and the mayor arrived, preceded by screaming red sirens, they shook hands, and then stepped onto The Avenue to watch the fife and drum corps play, and to pose for photographs.

Then it was into the lobby where African dancers performed for the mayor, the president and all of the crowd that pushed inside past Secret Service men.

During the buffet luncheon Toure, who met Barry in Liberia at the Organization of African Unity Conference last month, told the mayor that Washington, D.C. can serve African nations as an example of successful black majority rule.

Toure, dressed in white African robe and white slacks as were the others in his official party, said: "Progress in the United States can bring about change in Africa. We look at Washington, D.C., the federal capital, and we see that majority rule applies here, we see black leaders who welcome us and a City Council that reflects the will of the majority.

"This is a city where white Americans have never been oppressed or humiliated," Toure added through a French-speaking interpreter. "In South Africa you could have the same thing, majority rule with whites having the same dignity and the same freedom as other people."

Barry gave Toure, who began a week-long tour of the United States yesterday, a gold-colored key to the city and told him he remembered Toure from 1964 when the Guinean president invited Barry and other leaders of the Student Non-Violent Coordinating Committee, a sometimes militant civil rights group, to come to Guinea.

Stokely Carmichael, who later became famous as the head of SNCC, now lives in Guinea.

During his speech at the luncheon, Barry defended himself against critics who say his new international role has nothing to do with being mayor of the city.

"Washington is more than the monuments and the government buildings here," Barry said. "More than 700,000 people live here...this is the nation's capital and an international capital, therefore it is the proper role for the mayor to greet you."

In an interview after the luncheon Barry said he doesn't intend to use his new international stature to become a diplomat or national politician.

"I don't get anything out of this but personal satisfaction," he said. "I love being mayor and I intend to fill out the term of office...there's no higher office to run for in the District and I don't want to be president."

Barry met Toure as the Guinean president got off his airplane at Andrews Air Force Base yesterday morning and had breakfast with him at the Guinean embassy.

Toure then met with President Carter for an hour, although Toure is on a private visit to the United States seeking to attract business to his poor West African nation.

The president's meeting with Toure went beyond the usual courtesies accorded a foreign leader on a private visit and apparently was a signal of gratitude from the U.S. government to Toure for his recent drift away from the Soviet Union.

Toure and Carter discussed U.S. relations with Guinea and Guinea's influence on independent African nations, according to the White House press office. Toure's socialist country is one of the poorest in the world. Its 4 1/2 million residents earn an average of about $140 a year.

Later, in a meeting at the State Department, Toure discussed with Secretary Cyrus Vance the possibility of increased U.S. aid to Guinea.

After yesterday's luncheon here for Toure, which was paid for by mostly by local businessmen, Toure, Barry, and their 200 guests made their way back to Georgia Avenue. The crowds were still there, pointing at faces they recognized from newspapers and television.

"Man, they said that guy is the head of the Army," said a teen-ager as Secretary Alexander walked out of the hotel.

"Can't be," said his friend, another teen-aged youth. "The head of the whole Army. What was going on in there?" CAPTION: Picture, President Toure of Guinea accepts gift from Mayor Barry at Harambee House. By Vanessa R. Barnes - The Washington Post