Trump saw eight prototypes for his proposed wall, including one with blue steel on top. All eight models are between 18 to 30 feet high and 30 feet long. Four are made of concrete, while the others are made of alternate materials.
Building a wall along the border with Mexico was a central campaign issue for Trump, who said the wall will help fight drug trafficking and unauthorized immigration.
A rally of wall supporters is expected to take place, which has prompted heavy security to make sure there are no clashes between those for and against the plan.
"We are coming out here to support our president and show him that there are a lot of California Trump supporters here, and we are all coming together and banding together to let him know that we're here for him," said San Diego resident Amy Sutton.
WATCH: Protesters await President Trump's arrival in San Diego
Sidewalks along the U.S.-Mexico border have been designated as free-speech areas, where both groups will be converging.
"I don't think that the wall is going to stop people crossing the border. I think it's something that -- it doesn't have to do with the wall. It has to do with the culture in Mexico and the people, more than the wall," shared Fernando Toscano, a resident of Mexico.
There are reports of large containers that will be placed to block the view of people in Mexico seeing Trump, reportedly for security reasons.
"I came out because we're a country of immigrants and Trump is against everything our country stands for," said Diane McNelly, who was positioned with other demonstrators along what was believed to be part of the president's motorcade route. "He's a racist, misogynistic, and he's totally unqualified and inept. It just makes me sad to see it."
Trump was also briefed on lessons learned from the prototypes' construction and meet with border agents and officers to ask what they need, said Jonathan Hoffman, Homeland Security spokesman.
The president is determined to fulfill his campaign promise and will not be swayed by California Republican lawmakers concerned the wall is a waste of money, White House spokeswoman Sarah Huckabee Sanders told reporters Monday. She declined to say whether Trump would pick a winning prototype during his visit.
Later Tuesday, a protest organized by the political group Union Del Barrio is scheduled to take place in Beverly Hills ahead of Trump's arrival at the fundraiser, where donors will pay $250,000 to attend.