I have never heard of a strain called Puerto Rican and I have never heard of any strains that were native to Puerto Rico and no where else, thus making them Puerto Rican and not something like Jamaican that managed to make a short boat trip at some time or that might have been spread from island to island by sea birds or something.
The plants that appear to be the ones in question appear to be sativa dominant but they do not look almost pure or pure to me. Unless the actual strain can be positively identified and someone knows a generally accurate flowering period length to get you close so you can then check the trichome color to pick the very best time to harvest the best I could offer would be say that you are likely looking at 10 weeks or longer for total flowering time, rather longer is possible, and at 10-week begin to check your trichomes.
To be safe you might want to take an earlier check or two around 8 to 9-week but there is no way a sativa dominant plant is ready to harvest in only half to maybe one third of the length of time it will likely need to fully flower and mature.