Ronald Reagan campaigned for normally Democratic Hispanic and Jewish votes in his home state today with a declaration that "the Carter administration has mocked the promises it made to the Democratic Party -- indeed, to all Americans."

In east Los Angeles, the nation's most populous Mexican-American community. Reagan was introduced to an audience of about 100 Hispanics by state Sen. Alex Garcia, a Democrat. Garcia, who was supposed to endorse Reagan for president, stopped short of this but criticized the Carter administration and said that the Democrats had taken him for granted.

Outside the hall, a group of demonstrators that appeared to equal in number those inside shouted anti-Reagan slogans and waved signs that read: "Reagan Hates Hispanics."

Earlier, at an airport hotel, Reagan announced the formation of a committee of California Democrats and independents who support him. It is headed by Hershey Gold, an industrialist and prominent member of the Los Angeles Jewish community who served as national chairman for the 1976 presidential campaign of Democratic Sen. Henry M. Jackson (Wash.).

The Reagan Hispanic committee, organized under the title of "Viva Reagan-Bush," contains a smattering of Democrats who are fairly well-known locally. The effort is spearheaded by Al Zapanta, a former Ford administration official who is now a vice president of Atlantic Richfield.

"Carter has not delivered," Zapanta said. "He received 83 percent of the Hispanic vote in Texas and 75 percent in California but has not appointed Hispanics to many substantive positions. And there is huge unemployment in the barrio."