http://www.monster.com
click search jobs
scroll through until you hit: puerto rico-san juan
click enter and you will end up with listings all over
Puerto Rico.
I found a number of books at the library on Puerto Rico. I know that's soooooo old school but libraries rule! There is also a good possibility the information you gather there is a tad more factual than the average internet viewing.
If you like one of the books you read on the subject, they will have bibliographies thus giving you even more books to read. The other bonus is that alot of the books are written in english. They also could possibly help you think of careers/jobs in industries you would not have otherwise realized were there.
Chambers of Commerce can also be great sources of information. Some will even have a list of their members (and contact information) attached to their website. I know there is a least one in Puerto Rico -
http://www.camarapr.org/index_en.asp
Good luck!