Walter F. Mondale said today that the Reagan administration has "emboldened" terrorists with inconsistent statements about how it would respond to terrorism. He branded as "despicable" President Reagan's expressed doubts about Mondale's opposition to anti-Semitism.

At a news conference in the middle of a two-day California swing, Mondale said, "The worst thing you can do is talk in the abstract about what you would do about terrorism ."

He said that the open differences between Secretary of State George P. Shultz and Vice President Bush over policy toward terrorism exposes the White House as a "ghost ship" with no one in charge.

"All that theoretical talk yesterday, and the inconsistencies, only emboldens terrorists to think that this president doesn't know what he's doing," Mondale said.

Shultz said Thursday night in New York that "we must be willing to use military force" to combat international terrorism, and that "the public must understand before the fact that there is potential for loss of life of some of our fighting men and the loss of life of some innocent people."

Bush took issue with Shultz, but later softened his stand.

Mondale also said that no one has a better record in opposing anti-Semitism and that "we got a lot of things we can argue about but don't raise doubts among decent people about commitments as profound as that."

Reagan yesterday told a Jewish group in New York that the Democratic Party owed it an apology for failing to consider a resolution at its national convention condemning racism and anti-Semitism.

Earlier today in San Diego, Mondale prospected for the youth vote by warning, "If Mr. Reagan gets four more years, the far right will get five more justices. Don't let them have 'em."

At an outdoor rally of several thousand in San Deigo's Balboa Park, Mondale said, "In a strange and bizarre twist, these alleged advocates of a weaker government would use the power of the state to intrude upon the most personal and religious aspects of our lives."

"They want politicians to choose prayers for our children," he said to a chorus of "boos" from the crowd. "They want to impose religious litmus tests in the selection of federal judges . . . . They would seize our temple of liberty and turn it into an instrument of the Jerry Falwells of our time."

Mondale kept a light schedule this weekend, in part to gather strength for the final kick toward Nov. 6 and in part because he has adopted a less-is-more approach to campaigning here. "If we only give one speech a day, we know what's going to be on TV all over the state at night," said a staff member