I am not supporting Trump, his messaging on Puerto Rico is lame but what I heard reported is that the Sea Ports and the one open Airport have more traffic than they can handle and are working very hard to improve the amount of traffic they can handle.
Trump visiting will actually hurt more than it helps, it will take resources away from the recovery effort.
I am not saying that more could not be done but I am saying that that might be the case. They could drop food and water from Military Transports using parachutes like they have done in crisis overseas. It is wasteful and uncontrolled but it does provide some relief.
This is a triage type situation, someone is prioritizing efforts and aid, what is more important gas for generators or food and water. Going to need temporary shelters built but the builders will need shelters too. Do you let ships into port with food, water and gasoline or do you let in the ones that have the supplies to fix the docks and cranes so you can handle more ships.
In triage, someone has to pick winners and losers. The losers are going to complain, even the winners are going to complain.