U.S. presidential candidate Julian Castro joined dozens of high-profile Latinos in Puerto Rico on Monday to talk about mobilizing voters ahead of the 2020 elections and increasing Latino political representation to take on President Donald Trump.The group condemned Trump's plan to build a border wall, and Castro also criticized Trump for his response to Hurricane Maria, which hit the U.S. territory in September 2017 and is estimated to have caused more than $100 billion in damage."The administration failed to prepare for the hurricane, it failed to coordinate a swift response and has failed in the recovery process as well," Castro said. "What's worse, ... the president ... has talked about possibly taking money that had been earmarked for Puerto Rico recovery and instead investing that in a border wall. To do so is completely objectionable, immoral and should never happen."Castro spoke at the Latino Political Summit in the capital of San Juan, the third such summit organized by the Latino Victory Fund, a political action committee based in Washington, D.C. More than 20 federal lawmakers attended Monday's summit, attracting Trump's notice."A lot of the Democrats were in Puerto Rico celebrating something. I don't know, maybe they're celebrating the shutdown," Trump said.The visitors didn't include Democratic House Speaker Nancy Pelosi and Senate Minority Leader Chuck Schumer.Asked about Trump's comment, Castro said the lawmakers were doing "substantive work.""I wish that the president would actually spend more time doing the job of being president instead of fighting with people on Twitter, instead of spending so much time golfing and not going to his first meeting until 11 a.m. in the morning," Castro added.San Juan Mayor Carmen Yulin Cruz, a well-known Trump critic, said the president doesn't have the "moral footing" to talk about Puerto Rico."He came here for four hours and threw paper towels at us," she said in reference to his visit in October 2017 after Maria, when he lobbed paper towels to a crowd. "If you bring a clown to the White House, you're going to get a circus."Castro, the former housing chief for former president Barack Obama said his background helps him understand the process of recovering from a natural disaster and how to improve on that."This work is nothing new to me," said Castro, who also was mayor of San Antonio, Texas, for five years. The 44-year-old grandson of a Mexican immigrant so far is the only Latino in the Democratic field.Castro's first trip as a presidential candidate comes during the largest government shutdown in U.S. history, with Trump refusing to sign a government funding bill that doesn't include money for a wall on the U.S.-Mexico border.Mayor Cruz said the notion of a border wall was "racist" and criticized the administration's response to Maria."We were left to die by the U.S. government ... and we didn't have to die," she said, noting that an estimated 2,975 deaths have been attributed to the hurricane and its aftermath.Cruz also said she worried that Puerto Rico isn't getting hurricane recovery funds quickly enough as the island continues to struggle in the storm's aftermath."We need all the advocates that are here to go back to the United States and help us get the word out: The money isn't getting to the municipalities," she said.During the summit, Latino Victory Fund President Cristobal Alex said Trump has attacked Latinos, surrounded himself with white nationalists and separated children from their parents at the border."It's absolutely critical that we defend our community," he said. "We need to have representation. If you're not at the table, you're on the menu. We're working very, very hard to get a seat at that table."He said the Latino community is coming together like never before to step up against the U.S. president: "Donald Trump may prove to be the greatest Latino political organizer of all time."Castro and Cruz later toured the impoverished community of La Playita near the island's main international airport, where residents said they still need help more than a year after Maria.Community leader Raymond Ortiz, who owns a small store and helped feed people after the hurricane, told The Associated Press that more than 50 homes remain without a proper roof. He also said that nearly half of the people in the community have left because they didn't get the help they needed.