The presumptive Republican nominee took the stage in Anaheim, outside Los Angeles, with police on high alert one day after violence marred a Trump rally in the southwestern state of New Mexico, where anti-Trump protesters hurled rocks and police fired smoke grenades in efforts to rein in the chaos.
Dozens of security personnel including police on horseback maintained control in Anaheim, although some skirmishes broke out between Trump opponents and his backers as protesters chanted expletives about the brash billionaire. At least eight people were arrested.
Inside, Trump attacked his likely Democratic general election rival Hillary Clinton and railed against undocumented immigrants stealing US jobs.
But he insisted legal immigrants would vote for him in large numbers, despite polls showing they would overwhelmingly favor Clinton.
"The Mexican people are great, they're going to vote for me like crazy, the ones that are legally in this country," Trump said, as a woman waived a "Latinas for Trump" sign behind him.
- 'Too many immigrants' -Immigration is a flashpoint political topic in California. The state now has more Hispanic residents -- 39 percent -- than whites, according to the census.
"We have too many immigrants here, Mexican immigrants," Trump supporter Sharon Lombardi told AFP. "It's an invasion."
"Our cities are not the same," said Lupe Morfin, 58, adding that an "illegal alien" killed her 13-year-old nephew in 1990.
"Mr. Trump is the only one that would listen to us, and we love him."
Trump warned there would be "nothing but turmoil" and "four more years of Obama" if Clinton wins the White House.
"Our system and our country can't take it," he said.
Trump also insisted his "biggest strength" would be a robust national security, as he lambasted countries like Germany for allowing refugees to flood into Europe unchecked, increasing the terror threat.
"All over Europe they're taking these people and all over the United States they're sending these people," Trump said. "How stupid are we? This will come back to haunt us."
Several Trump rallies have drawn protests, including one in Chicago in March when his supporters clashed with protesters.
Trump described his Tuesday rally in Albuquerque as a "love fest," even though the chaos outside left several officers injured.
In his speech in New Mexico, which has the highest percentage of Hispanic residents of any US state, Trump startled observers by criticizing Governor Susana Martinez, the nation's only Hispanic governor and head of the Republican Governors Association.
"She's got to do a better job, OK?" Trump told the crowd about Martinez, who has criticized Trump's remarks on immigration and was absent from Tuesday's event.
- 'Will not be bullied' -It was the latest example of behavior that may compound Trump's efforts to win over skeptical voters. Martinez is seen as someone who could help a Republican nominee win support from Hispanics and women -- on her home turf, saying she was not cutting it as governor.
Martinez's office responded swiftly, saying the governor "will not be bullied into supporting a candidate until she is convinced that candidate will fight for New Mexicans."
The blunt response highlights the tensions within the party even as it prepares to crown Trump as its nominee.
House Speaker Paul Ryan -- the nation's top elected Republican -- said he was not yet prepared to endorse Trump for president.
"I haven't made a decision," Ryan told reporters, two weeks after he met with Trump to discuss ways to unify the party behind his remarkable White House run.
Former House majority leader Tom DeLay had choice words for the presumptive nominee, calling Trump's criticism of a popular conservative Latina "stupid politics."
"It blows my mind," DeLay told MSNBC. "Where is he going to get his coalition to win?"
Following his Washington state victory, Trump has now amassed 1,229 delegates, according to a CNN tally -- just eight shy of the 1,237 needed to clinch the nomination.
He is expected to cross the threshold June 7, when California and four other states vote on the final day of the Republican primary contest.
Trump pivoted to the general election weeks ago, relentlessly criticizing his likely Democratic rival.
The former secretary of state has returned fire, although she is still engaged in the final stages of her Democratic battle against Sanders.
On Wednesday, the scandal over her use of a private email server while secretary of state resurfaced, with a starkly critical report by the State Department's inspector general finding she had not sought permission to conduct official business on her personal account.