As a beach walker and trash-picker-upper whenever I am on the local beaches, I suggest the best time of year to conduct beach clean-ups is winter, not summer.
After heavy rains and stormy seas, that's when all the plastics and spray paint cans and bits of polystyrene are strewn all over our beaches. I understand there may be more than one Cleanup Day per year, but winter cleanups would be more effective.
Also: why aren't the lobster fishermen held accountable for their "lost" traps? I see these traps often, along Hendry's and other beaches. There is almost always some kind of plastic rope attached, and a plastic dish within the trap. These plastics break down with each high tide, if the trap is up on the sand. Lobster traps are litter, too. Have the lobstermen put their i.d. on their traps, and make them come retrieve them off our beaches.