I do not believe that this law will pass Constitutional muster. There is a doctrine called "pre-emption". Think of the Constitution as a "contract" between the states (and for this purpose, Puerto Rico is a state). There are powers granted by the states as a group to the federal government and Congress can regulate an industry on a national basis, totally forclosing the states from making further rules on the subject. Courts have consistantly held that broadcasting is such an industry. The FCC makes ALL of the rules on that subject, states cannot make additional ones.
This would clearly go to court, not a Puerto Rican court, but the US District Court for the District of Columbia, and the appelate courts up from there, for years.
Further, it would be a simple matter for DISH to simply "sell" its Puerto Rican operations. Either legitimatly or to a dummy company, and thus avoid the issue.
The realtiy, of course, is that a little geographic and economic knowledge goes a long way. The Earth is round. Puerto Rico is 1000 miles further away from the signal than the mainland. Puerto Rican per capita income in 64% of that of the poorest state and about 55% of the national average. Pay TV is a luxury item that depends on disposable luxury income. According to the University of Puerto Rico, 97% of Puerto Ricans speak Spanish as a first language and, while 90% have at least some knowledge of English, 95% do not speak "fluent" English. DISH is a provider to TV services, the majority of which are in English.