Barbara, I neither work on statistics of earthquakes nor do I read any/many scientific articles about tides vs earthquakes, but I think the entry you quote almost certainly is false false false. John Vidale does work on these things and he has repeatedly posted that there is only a tiny effect (and I think it needs special conditions). Yes, I am aware of the Tolstoy article on speading center seismicity correlated with earth tides (?) but have not read this. When you are talking about M7s and a huge significance (60% during 14% of year at maximum tides) it is really very easy for someone who works in the field to check this.

So, I'll argue that Puerto Rico is near/along a plate boundary, so like California is prone to quakes, but that there is about zero reason to think that you will get a large quake in a particular week. So, enjoy the trip, but if you do happen to have a quake that shakes for a minute or longer, get away from the beach....and as fast as you can.
Chris