Hot plates were brimming with paella and burritos, a folksinger strummed a guitar and sang in Spanish, and travel posters of Latin America were pinned to the walls as 135 U.S. Labor Department employes gathered at noon yesterday to commemorate National Hispanic Heritage Week.

They shared stories and food, and assembled in an auditorium to hear the thoughts of the District of Columbia Superior Court's first Hispanic judge, Ricardo Urbina.

Urbina, in a speech at the Patrick Henry Building, 6th and D streets NW, called for increased voter registration, political education and activism in the Hispanic community.

"I remain firmly convinced that in 20 years or less, Hispanics can become the strongest minority voting group," said Urbina. "Those of us who understand the system have an obligation to be the most active.

"Our mission of occupying a position in the mainstream of American life is more than a mission. It is an obsession."

Urbina said Hispanics in the United States suffer from poor housing, unemployment, inadequate educational oppotunities and insufficient political representation. He called on Hispanics to help in voter registration drives and in the political campaigns of Hispanic candidates.

Urbina also said "The vision of Hispanics piped into our living rooms via television is a depressing statistic." Hispanics generally are either ignored on television or portrayed as "criminal types," he said.

Urbina, who was nominated to the Superior Court bench by President Carter toward the end of his administration and then renominated by President Reagan, said in an interview after his speech that judicial ethics prevented him from commenting on either of the past two administrations' efforts in Hispanic affairs.

Urbina's appearance, and the luncheon that preceded it, was sponsored by the Hispanic American Cultural Effort, an employes group in the Department of Labor.

There are an estimated 70,000 Hispanics living in the Washington metropolitan area, and 14.6 million -- or 6.4 percent of the population -- living in the United States, according to the 1980 census.

National Hispanic Heritage Week, which began last Sunday, was initiated in 1968 by an act of Congress. In his proclamation of this year's celebration, President Reagan paid tribute to the "Hispanic explorers, pioneers and settlers who have helped shape this vast land."

The Congressional Hispanic Caucus, chaired by Rep. Robert Garcia (D-N.Y.), is scheduled to conclude a two-day seminar on Hispanic issues today, and federal agencies, including the Departments of State, Agriculture and Interior have special programs.