President Reagan, whose administration has made Hispanic voters a prime political target for 1984, yesterday observed Hispanic Heritage Week by naming Katherine Ortega treasurer of the United States.

"She was the first woman president of a California bank, so you can see that she's being nominated not just because she is Hispanic, but because she is highly qualified," Reagan said in a ceremony attended by Hispanic leaders in the East Room.

Ortega, her eyes filled with tears, stood at Reagan's side as he announced the nomination, which she said she accepted "with a deep sense of joy, pride and gratitude."

"I have often said I was born a Republican," said Ortega, 49, a businesswoman whose father was a blacksmith in New Mexico. "I am the product of a heritage that teaches strong family devotion, a commitment to earning a livelihood by hard work, patience, determination and perseverance."

Ortega, the youngest of nine children, is the second Hispanic to serve in the treasurer's post, which traditionally has been filled by a woman. The first was Romana Acosta Banuelos, who was appointed by President Nixon in 1971.

The Reagan administration has made Hispanic voters a high priority in the president's anticipated reelection campaign next year.

The prevailing political wisdom in the White House is that Reagan must win at least 30 percent of the Hispanic vote, about what he got in 1980, to offset anticipated Democratic gains among black voters.

The Hispanic vote is considered a key factor in three populous states--California, Texas and Florida--regarded as "must win" states in a Reagan reelection campaign. White House chief of staff James A. Baker III, a Texan, had strongly urged that the president name a Hispanic woman to the treasurer's post, according to administration sources.

The president claimed in his speech that 125 Hispanics already hold posts in his administration and said that another 20 to 25 soon will be appointed. After disclaiming that Ortega was nominated primarily because she is Hispanic, Reagan paid tribute to "the increased participation of Hispanic Americans in all phases of the political process."

"And let me say wholeheartedly nothing is a better influence on America than the strength and decency of the Hispanic family," the president added.

Ortega, a certified public accountant, became the first woman bank president in California as head of the Santa Ana Bank. She currently serves as commissioner of the Copyright Royalty Tribunal.

If confirmed by the Senate, Ortega will succeed Angela (Bay) Buchanan, who resigned recently and will serve as treasurer for the Reagan reelection campaign committee when it is formed next month. The East Room ceremony marked the first of six events that Reagan will attend this week in honor of Hispanic Heritage Week. It is the second week in the past month that he has emphasized the importance of Hispanics.

Earlier yesterday, Reagan addressed a group of local officials meeting at the Capital Hilton Hotel and said that his administration was "getting the federal spending and taxing juggernaut under control."

Sounding themes that were staples of his political campaigns of the past, Reagan criticized federal regulations and bureaucracy and asserted that "local government across the country is proving itself efficient and responsive to the will of the people."

"If it was ever true that federal employes had greater capabilities than their local counterparts, those days are rapidly coming to an end," he said in a speech to the National Association of Towns and Townships. "Today modern technology is opening up greater and greater opportunities for state and local governments."

Reagan maintained that in transferring programs "back to levels of government closer to the people," his administration also was giving them "the resources to get the job done."

However, many states and municipalities have complained that administration budget cuts have left them with greater responsibilities, particularly for social services, but with less funds for them.