Ordinary construction debris and household junk are fine. The limits come from commonwealth law and from what the receiving site will accept.
Puerto Rico law bans the deposit, disposal, and storage of coal ash and coal combustion residuals anywhere on the island, and it carries penalties. That rule has been enforced across the southern towns, so nothing of that kind can ride in a container.
Hazardous waste, liquids, paint, solvents, fuel, used oil, and asbestos are kept out of ordinary disposal under the commonwealth's solid waste rules. Those rules are written and enforced locally rather than by federal staff, which means the receiving site, not a federal office, has the final word on a questionable load.
Tires, batteries, and large appliances should be set aside and mentioned when you book. Each has its own handling route on the island, and a single one mixed into a load can get the whole container turned away at the gate.
Recycling is also part of the picture. Coamo runs its own recycling department, and the disposal sites serving this area operate under required recycling and composting programs. If you can keep clean block, concrete, and metal separate, do it. Ask your account manager what belongs in which load.