The sidewalk in front of the United Planning Organization (UPO) headquaters at 14th and L streets NW became a stage last week for mime artists, young photographers and youngsters, dancing and chanting street games.

Nearly 300 youths and communty leaders came to represent 17 of the city's 20 Neighborhood Planning Councils (NPC), federally funded job-training and cultural enrichment program for poor youths 13 to 21 years old. NPCs are funded by the federal government through UPO.

The marchers called it a "fair", but the signs they carried reading, "UPO we're no joke. Don't forget about us poor folk," told the real purpose of the peaceful, two-hour demonstration organized by the NPCs. The participants had come to protest UPO's proposed funding cuts of the NPCs.

In recent weeks, Walter Lewis, president of the UPO board, has said that UPO would decrease its 1979 discretionary grants to the NPCs and other programs because the funds are needed for pay increases to UPO personnel and to expand adult employment programs. Lewis declined to say how much the cuts would be.

Over the years, UPO has lost private and federal grant funds, Lewis said, and the limited funds now available must be spread over more activities.

The NPCs contend, however, that'is time to change those funding methods.

Neil Seldman, a professor at George Washington University and an officer with NPC 8 in the Adam's Morgan area, said the NPCs are working on a proposal for direct funding from the federal government.

"UPO is paying no attention to us," said Seldman, "and we want out after Oct. 1," the date the 1979 funding year begins.

Throughout the demonstration last week, community leaders and youth spoke of the problems of youth employment in Washington and the possible effect of cutting NPC programs.

Patricia Bernard, 16, and Jennifer Wilson, 18, who tutor youths at the NPC 9-sponsored Clifton Terrace Reading and Math Center in Northwest Washington, said they work with children like Anthony, a 9-year-old fourth grader who can't read or write.

"What will happen to Anthony if NPC funds are cut?" the girls asked.

Bernard and Wilson, along with other youths who work for NPCs, said they could not have gotten jobs without the NPCs. Wilson said they applied for jobs at area restaurants, fast food chains, drug stores and department stores, "but they wouldn't have us because we didn't have enough work experience."

The UPO funding cuts along with inhouse politics are continually decreasing NPC jobs, added Charlotte Fillmore, chairperson of NPC 8.

Fillmore, an energetic woman who has woked with area youths for more than 14 years, chartered a Metrobus, "out of my own pocket," to bring nearly 50 children to the fair from her childhood development center in Adams-Morgan.

During the past two years, Fillmore said, they youths in her area have been unable to get NPC job applications processed at the Cardozo High School job center.

"They (the center personnel) lose the applications and they're saying the parents make too much," said Fillmore, who added that the children of one of her center instructors had been turned down by NPC.

The instructor, Lee Brooks, has five children, all unemployed teen-agers, who couldn't get NPC jobs this year. Brooks said her own position became part-time because of the funding cutbacks at NPC. Her family lives on her salary and on disability payments her husband receives from Social Security.

"I stretch my husband's check as far as it can go," said Brooks. "We don't have a whole lot though."

Besides supplying jobs, NPC leaders and youths said the NPC recreational programs keep aimless youths off the streets and help them expand work and cultural interests.

One NPC student, Fran Scott, 17, recently received a college scholarship to study photography at the Rhode Island School of Design. Both Scott and Chris Aldridge, 16, a student at the Duke Ellington School of the Arts, credit their photo-journalism skills to working on Cityspace, the NPC-funded urban magazine. Cityscape has won a Robert F. Kennedy award and recently became the subject of a Canadian documentary film, said Ellington instructor Margaret Stevenson.

"There's just not enough programs like this in the city," added Lillian Smith, a volunteer with the NPC in Anacostia for 10 years. "We have four programs in our area. We need 10 more. Our youth want clerical skills, photography, nursing, but we just don't have the money to fund these kinds of programs."