The White House has published few additional details on the president's visit including who will be among the estimated 1000 attendees to welcome Obama at Muniz air force base. It's also unknown what topics he may discuss with Gov. Luis Fortuno such as Puerto Rico's future political status or the island's stagnating economy.
As Roque Planes of the Americas Society wrote, the timing of Obama's visit may have more to do with voting Boricuas residing on the mainland than those living on the island:
Obama may have other reasons for timing the trip this month. The Latino vote proved key for Obama during his 2008 campaign, but he has moved slowly to address immigration reform—one of the constituency’s highest priorities. Shortly after formally announcing his reelection bid in April, Obama began aggressively reaching out to the Hispanic leadership. He held well publicized meetings within weeks with high-profile stakeholders including media mogul and New York City Mayor Michael Bloomberg, actress Eva Longoria, and journalist José Díaz-Balart. He renewed his call for the DREAM Act during a commencement speech at Miami Dade Community College on April 29 and he called for comprehensive immigration reform at El Paso on May 10.Obama last visited Puerto Rico as a presidential candidate in 2008 though his trip tomorrow will mark the first by a sitting U.S. president in fifty years. President John F. Kennedy traveled to the island in 1961 and in the video snippet below he received a warm welcome from Gov. Luis Munoz Marin:
Video Source - YouTube
Online Sources - primerahora.com, NY1, Politico.com, AS/COA Online