I bet 99% of their constituents don't even know what the Jones act is or would be perfectly willing to change it.
That's a bold claim. On what are you basing the assumption that many or most Democrats would be willing to change the Jones Act, if they knew what it was?
It's not particularly bold to assume that convincing Democratic voters to repeal an obscure law that the AFL-CIO vehemently supports is an uphill battle.
There is literally zero evidence that members of AFL-CIO unions oppose the AFL-CIO's persistent lobbying in favor of the Jones Act. There's plenty of evidence to the contrary, namely (1) the fact that it serves their own interests, and (2) the fact that there has been zero opposition to it over the last century that the AFL-CIO has supported it (in contrast to the example you site).
Given how heavily certain group lobbied to prevent the government from issuing just a temporary waiver after Hurricane Maria, I wouldn't bet on this happening anytime soon.
Democrats support the Jones Act because their core constituents do. Republicans have a complicated history with lobbying for Puerto Rican issues. So neither party has an incentive to fix it, and neither party sees Puerto Evans as constituents.