SAN DIEGO - President Donald Trump on Tuesday got his chance to inspect prototypes for the "big beautiful border wall" he wants to build to separate the U.S. from Mexico, saying strengthening the border would help stop "99 percent" of illegal immigration ó or, he allowed, "maybe more than that."The president, making his first trip to California as president, appeared engaged as he was briefed on eight border wall designs. He said he preferred a fully concrete wall because it was the hardest to climb, but he noted that it needed to be see-through.Trump said the first thing he noticed on the drive to view the prototypes was the patched-up holes in part of the existing fence at the border."We have a lousy wall over here now, but at least it stops 90, 95 percent," Trump said. "When we put up the real wall, weíre going to stop 99 percent. Maybe more than that."Trumpís visit was greeted with peaceful protests by demonstrators both for and against his planned wall. The trip also came amid an escalating battle between his administration and the liberal state, which has refused to help federal agents detain immigrants in the U.S. illegally.The president said Tuesday that the stateís sanctuary policies "put the entire nation at risk." His Justice Department sued California last week over a trio of the stateís immigration laws."Theyíre the best friend of the criminal," Trump said. "Thatís what exactly is happening. The criminals take refuge in these sanctuary cities and itís very dangerous for our police and enforcement folks."While in California, Trump was also expected to address Marines in San Diego before attending a high-dollar fundraiser in Los Angeles, where heíll stay overnight.Demonstrations were held at the San Ysidro port of entry in San Diego, the nationís busiest border crossing, where protesters chanted, "No ban! No wall!" as honking cars and buses cheered them on. Protests were also held on the Mexican side, in Tijuana.At San Ysidro, Jose Gonzalez, 21, stopped to snap a photo of the protesters holding signs, including one that read: "Wall off Putin!" in reference to Russian President Vladimir Putin, who has a seemingly close relationship with Trump."I donít think itís really fair how he has the choice to separate us," said Gonzalez, a dual citizen who lives in Tijuana and crosses the border daily to work at a San Diego ramen restaurant.Army veteran Mark Prieto, 48, shook his head as he walked by the protest."People are so narrow-minded," the Riverside firefighter said as the crowd chanted. "Finally we have someone who is putting America first."His wife, Corina Prieto, a nurse who has extended family in Mexico, agreed. Both voted for Trump."I think he is doing a lot of good, like protecting our Border Patrol," she said.Trump was to be briefed on lessons learned from the construction of the prototypes built in San Diego last fall. He was also to meet with border agents and officers to ask what they need, Homeland Security spokesman Jonathan Hoffman said.San Diegoís Republican mayor criticized Trumpís planned short visit, saying the president wonít get a full picture of the city. Kevin Faulconer said a popular cross-border airport terminal connecting San Diego and Tijuana shows that "building bridges has worked wonders."Faulconer, writing in The San Diego Union-Tribune, also said San Diego police work to protect everyone regardless of immigration status, an apparent dig at Trumpís push to target illegal immigration.Trump tweeted about Californiaís immigration policies as he flew to the state aboard Air Force One."Californiaís sanctuary policies are illegal and unconstitutional and put the safety and security of our entire nation at risk. Thousands of dangerous & violent criminal aliens are released as a result of sanctuary policies, set free to prey on innocent Americans. THIS MUST STOP!" he wrote.This isnít Trumpís first visit to the border. He traveled to Laredo ó one of Texasí safest cities ó weeks after declaring his candidacy in June 2015.Trump told reporters then that he was putting himself "in great danger" by coming to the border. But, he said, "I have to do it. I love this country."