This is it, right here, the Great American Dream. Here is Abelardo Lopez Valdez, the man who will introduce royalty to Jimmy Carter, the man who must see that Menachem Begin gets fish and King Hussien beef, this man of manners and pinstripes. This man, well, this man was a migrant who picked cotton in Texas and beets in Montana.

Never, ever would you guess this about the new State Department protocol chief. He is urbane, sophisticated. He went to Harvard. He has been a lawyer, an engineer, and a military officer. He wears collar pins.

But Valdez will tell you right off, and proudly, that he was a migrant in Floresville, Tex., (pop: 3,500) who worked his way up to oversee a $450-million Latin American aid and development agency at the State Department. And now, he's expected to be confirmed as ambassador and protocol chief to oversee state visits -- a largely ceremonial job that has traditionally gone to the rich, to the well-connected, or both.

"I don't think that wealth ought to be the requirement for any job in this country," he says. "It goes against the grain in America."

Valdez is patriotic without a hint of embarrassment because America, for him, has been that land of opportunity scoffed at by skeptics.

He is full of stories about the cotton picking, about the time in Texas his family lived in a hay storage hut near a cattle corral, about the jobs he held in high school that put him through Texas A & M and Baylor University. Later, he would get a fellowship for Harvard Law and a scholarship to the Hague Academy in the Netherlands.

"I had parents who were very determined that their children would /ave as much education as possible, even under the worst circumstances," he says. "And as for me, I've worked hard all my life. There is no substitute."

When he takes over the $50,000-a-year job (probably at the end of this month) that was vacated by Kit Dobelle when she became Rosalynn Carter's staff director, Valdez will be the highest-ranking Hispanic in the State Department. Many see this Carter appointment as an undisguised political move, designed to increase the president's support among the nation's estimated 20 million Hispanics.

Which is a suggestion that clearly annoys Valdez as he sits in his mostly brown and mostly sterile office at the State Department. "I don't feel I have to apologize in any way for being appointed to this job, or for being an Hispanic," he says. "The primary reason I took it is because the president asked me to take it. When he asks you to do something, you have to have a very good reason to say no."

And then Valdez, 37, ticks off the last of his qualifications; lawyer, specializing in international trade, Washington; faculty member, teaching a seminar in U.S.-Latin American relations, Harvard University; assistant administrator, the Agency for International Development, the State Department; and social aide during Lyndon Johnson's administration, the White House.

His friends add charm, then ambition, to the list. The charm is easy to see. Tall, dark and handsome, three too-often used words, really do belong to him. He has dimples. And a sort of formal grace, too. Emily Post would have branded him gentlemen.

His friends call him Lalo, and he lives with his wife Margarita in Northwest Washington. She is a native of Bogota, Columbia, and is not yet an American citizen. She met her husband at a New Year's Eve party in 1976, works for the Inter-American Development Bank, and plans to help with the protocol duties in some capacity.

As for her husband's ambition, it's a quality not quite so easy to see as the charm. But friends and business associates insist that it's there.

"I would think the protocol job would have something to do with his aspirations, policitally, for bigger and better things." says Keith Miceli, executive director of the Association of American Chambers of Commerce in Latin America. "I would think the job would give him a lot of exposure. It would be to his advantage -- and the advantage of his political group."

Valdez denies the talk of personal political advantage, but supports his position as one to benefit Hispanics. "I think it's important that Hispanic Americans not be stereotyped into work that is only on the poverty level," he says. "It's important to convince Americans we can do any job.We need representation in all levels and in every department."

Valdez has been a strong, vocal supporter of Hispanics in his job at the State Department -- so vocal, in fact, that some say he created a good deal of resentment there. "He's made enemies, even in the Agency for International Development," says one business associate. "That's because he hasn't gone out and played the bureaucratic game of accepting budget cuts that are dictated from above."

But Valdez, son of a Mexican immigrant, says he had no qualms speaking out for money to Latin America. He gives Carter a large part of the credit for the increase in aid to that part of the world, which now stands at $450 million a year.

Valdez also praises the president for appointing more than 100 other Hispanics to all levels of government jobs. (This is including last week's promotion of Edward Hidalgo, a native of Mexico, to replace W. Graham Claytor Jr. as secretary of the Navy.)

Like the others, the Valdez appointment to protocol has drawn a positive reaction from the Hispanic-American community. "I'm really very impressed," says Alejandro Orfila, the secretary-general of the Organization of American States. "He has proved to be an extraordinary man with great common sense. He has just everything that is needed for chief of protocol."

Having "everything" apparently includes dancing, which Valdez says he likes. He also has a fondness for reading history and biographies, playing tennis and swimming. And Ambition? Yes, he admits, he has that too.

As he puts it: "I don't think you could go from being a cotton picker to where I am now without a little bit of it."