WHEN WASHINGTON has its annual Hispanic showcase fiesta on Columbia Road this Saturday, it will again demonstrate that Washington has a burgeoning Spanish-speaking population of astonishing diversity. Twenty-four nationalities will be represented, ranging from Panamanian blacks to blue-eyed Colombians, from Nicaraguan Catholics to Chilean Jews, and from Cubans who thank God every night for the existence of Ronald Reagan to Salvadorans who sympathize with their country's rebels.

What will be absent from this fiesta -- as in the past -- is any genuinely local Hispanic political leaders. What passes for that in Washington is actually a group of New York Puerto Ricans who know only by reference some of the key watershed experiences of this Hispanic community. As U.S. citizens from birth, these would-be chiefains have never, for example, had their names on file with the Immigration and Naturalization Service, living in fear of deportation. For many, in fact, English is their first language and their Spanish is not all that good.

That difference in background and perspective is the key liability facing the community as well as its political hopefuls in the city -- who lately have taken to sparring head-on with Mayor Marion Barry.

Granted, the local Hispanics make a poor political base, given their roughly 2,000 votes in a Spanish- speaking population perhaps 30 times that. But their ambitious out- of-town ward heelers have so far become either colossal embarrassments or found themselves alone tilting against the windmills with no visible reward accruing to those they are titularly leading.

The heads of storefront aid organizations, ostensibly led by Enrique Rivera, recently voiced community needs as they see them in a Latino Community Agenda they presented to Mayor Marion Barry. But they are not leaders as much as they are purveyors of services funded by the city for a client population that happens to be Hispanic. They are hardly, as they claim, independent advocates from the heart of the community.

Much the same is true of the largely ineffectual Mayor's Office of Latino Affairs. Barry's first appointee to head OLA (which cutely sounds like "hello" in Spanish) was Willie Vazquez, a Puerto Rican import from the Bronx with little history in the District.

His successor, Arlene Gillespie, also a Puerto Rican outsider, has tried desperately to gain acceptance in the Hispanic community from her well-appointed office on Belmont Street in Adams-Morgan. But the most notable of her efforts was to have herself locked up by D.C. police after she "symbolically" pretended to speak only Spanish when she was arrested at the South African embassy for picketing against apartheid.

Positively the most dramatic case so far is that of Jose Gutierrez. Gutierrez became the highest ranking Hispanic city official in Washington. He rose to D.C. director of personnel in 1981 and later was shifted to director of purchasing. Yet not a word was heard from Hispanics at large following his precipitous fall weeks ago.

When Barry demoted and later fired him, alleging that Gutierrez had dealt sweetheart contracts to the construction firm of Roubin & Janeiro -- a member of the Hispanic Chamber of Commerce -- Gutierrez' former community allies deserted him. Typically, Gutierrez had earned his political merit badges not here, but in New York, working for Herman Badillo when he ran for mayor.

Ultimately, Gutierrez was a victim of his own vulnerability as an outsider without a real political base. Unlike the Bronx, the Washington area does not have a rooted Latin community spanning at least two generations. Most Washington Hispanics are either highly educated diplomats, or "non-immigrants" who work in international organizations or poor, undocumented or in any case recent immigrants from Latin America who generally can cite the very day and hour they first arrived.

Tallied at roughly 60,000 in the District and estimated at up to 200,000 throughout the metropolitan area, many speak primarily Spanish and only a smattering of English, and are still struggling to make a home here. To them the comings and goings of city officials, Hispanic heads of social service agencies and Hispanic merchants are utterly trivial.

Hispanics here are, of course, organized around their specialized interests. For example, recent refugees from Central America -- said to be arriving in staggering numbers -- cluster around emigre organizations such as Casa El Salvador or the Central American Refugee Committee, whose Spanish acronym CARECEN spells out "those who lack" in Spanish. Their politics are, at heart, related to foreign rather han municipal affairs.

Business people, a small minority among Hispanics, have their Ibero- American Chamber of Commerce, whose members collectively gross several hundred million a year. Indeed, Dominican Daniel Bueno, owner of the Zodiac record store in the Adams-Morgan neighborhood, is the president of the upcoming Columbia Road festival's organizing group and the promoter of Caribbean singers Celia Cruz and Willie Colon, who are scheduled to perform at the event.

Bueno and his colleagues say they represent Hispanic private initiative; others call it greed. They deserve credit for hosting a good party and shaking off the Byzantine behind- the-scenes "politics" that haunted the festival for 13 of its 15 years. But such a group is far from seeking or earning the community's political helm.

Hispanics who need help appeal to tens of small storefront groups such as Ayuda, a legal aid group, or Andromeda, a mental health service. As soon as their need is filled, as tired case workers will vouch, the Hispanic clients will go on with whatever life they had before. They may be grateful, but they do not linger like convalescents around their helpers once the problem has been solved.

What Washington's Hispanic "leaders" are almost without exception New York Puerto Ricans is explicable. It makes sense that a group of Hispanics who have integrated into the American mainstream, yet retained a sense of their identity as Hispanics, would be the first ones to carry some clout.

But still, Hispanics in D.C. have a long time to go before one of their own, having struggled with and been present for the community, can legitimately lay claim to the mantle of leadership. Meanwhile, the current head honchos will remain weak caricatures of such an individual.