Scenes from a neighborhood in transition:

At the corner of 10th and M streets NW, three dozen Hispanic men gather outside an apartment building on a warm afternoon, playing cards, listening to Spanish-language songs, talking. Across the intersection, young white people go in and out of a glitzy new apartment complex.

Two blocks north, another group of Hispanics plays soccer, running up and down the length of the grass-and-dirt playground at Shaw Elementary School, while black youths play spirited basketball games on the adjacent courts.

During the last two years, Northwest Washington's Blagden Alley neighborhood -- an area that includes Ninth and 11th streets and Rhode Island and Massachusetts avenues -- has taken on a distinctly Latin flavor as a growing number of Hispanics have moved there in search of affordable housing.

In the process, several apartment buildings in the area have become almost completely Hispanic.

At Thompson Elementary School, at 12th Street and Massachusetts Avenue NW, the number of Spanish-speaking students in the bilingual education program has grown steadily, from 80 in the 1987-88 school year to 101 in the 1989-90 year, and is expected to rise again this year.

The influx has further diversified what already was a polyglot neighborhood, one that is home to longtime black residents and "thirtysomething" white professionals drawn to its relatively affordable row houses.

It is part of a broader pattern in which Hispanics, who traditionally have been concentrated in the Mount Pleasant and Adams-Morgan areas, are dispersing throughout the District in search of lower-cost housing as their old neighborhoods become gentrified and pricey.

Those movements are certain to pose new challenges for area schools, city services and other residents, officials say.

Such challenges already are evident in Blagden Alley. In a sense, many of the new Hispanic arrivals are not yet part of the neighborhood, keeping to themselves and having little contact with longtime residents, few of whom speak Spanish.

"We communicate by waving and that's it," said Suzanne Aebersold, a Ninth Street resident and member of the Blagden Alley Association. "We'd like to get to know them better, because they're a significant part of the community."

One of the reasons for the swelling Hispanic population is an informal but remarkably effective word-of-mouth network that has spread news far and wide about the area's affordable apartments. One-bedrooms in the neighborhood typically rent for about $400 a month.

Jose Santo Lemos, 30, a Salvadoran immigrant, was living in Fresno, Calif., a year ago when his girlfriend's brother told them about an inexpensive place in Washington to live -- an apartment building in the 900 block of N Street NW. Lemos and his girlfriend came East and moved into the building, and Lemos now works in a Capitol Hill restaurant.

"It's nice here," Lemos said as he and several other Salvadorans lounged on the small front porch of their building. "You can speak among people who speak the same language as you."

Many of the Hispanics who have recently moved into the neighborhood hope that their new, usually modest accommodations are a way station to even better ones.

Rodrigo Salvador, a bakery employee who lives with his wife, Esther Maria, and their two young sons in an apartment on 10th Street, pointed to a new building down the block.

"I can't go live there because I don't make enough money," he said. "We can't find a better place to live because of economic reasons."

In general, neighborhood activists and longtime residents are supportive of the new arrivals.

There are problems, too, many of them rooted in cultural differences.

The manager of a more expensive apartment building near 10th and M streets said her tenants often complain about Hispanics congregating noisily outside a building across the street. Others are annoyed by heavy public drinking and litter problems that they say have been created by some of the new residents.

Those kinds of problems stem from cultural differences, said Rita Soler Ossolinski, acting director of the city's Office of Latino Affairs.

"It's natural to socialize outdoors in most Latin American countries," said Soler Ossolinski, who noted that drinking in public is not against the law in many of them. She also said that many of the newcomers have emigrated from countries where sanitary standards are not as stringent as in the United States.

"You have to educate the people who were there first as to who these people who have moved into their neighborhoods are," she said. "We also have to educate the new arrivals that you cannot drink in public, you cannot blast your radio as loud as you want, you cannot urinate in the alley."

Rodrigo Salvador acknowledged that the socializing in front of his apartment complex and the building next to it is sometimes too noisy. "There's no air-conditioning {in the apartments}, so when it gets very hot people go outside," he said.

But not everyone is critical of the gatherings. The Aebersolds and some other neighbors said they believe the outside presence discourages criminal activity that might occur on a quieter street.

One of the few non-Hispanic residents of Salvador's building agreed that the noise is a nuisance, but a relatively minor one.

When such gatherings occur at night, "You can't sleep at all," he said.