Well, since nobody has replied, I thought I'd post what I have found so far for future rockhounds.
Apparently, amber is pretty prevelant throughout the Greater Antillies. It is mainly concentrated in the Dominican Republic, but can be found in Puerto Rico and Cuba. The rare blue amber (http://en.wikipedia.org/wiki/Blue_Amber) is mainly concentrated in the central region of the Dominican Republic, but can (rarely)be found on the beaches of Cuba and PR.
Here is a free article, "Geology of the Amber-bearing deposits of the Greater Antilles" from vol 31 of the Caribbean Journal of Science. There is a small amount about PR and a lot about the rest of the islands.
The Southwestern tip of PR seems to be where a lot of minerals are at. The Univ. of PR's geology department is at the Mayaguez campus (southwestern tip). Here is their website: http://geology.uprm.edu/ , however, I did not find much useful information on it.
Here is a link to another board of a guy who went to PR and he sorta describes what he found:
That's it for now. Hopefully this will help someone else, and I will post more if I find it!