Hi, I toured puerto rico a few years back (2008) with my girlfriend. Our goal was to cicumnavigate the island starting from san juan we went clockwise around the island making stops at the island of culebra, and el yunque rainforest. We thought it would take us much longer because we overestimated the size of the island so we ended up taking our time and split the bike trip over 7 days or so. We were in PR for 2 1/2 weeks.

If I could do it again I would start from san Juan and then go counter-clockwise around the island to the southwestern tip. Arecibo, isabella, and Auguadilla were really nice (surf) towns. You must go to the Los Morrillos Lighthouse on the southwestern tip the salt flats there were unbelievable At La Parguera you can take boat tours out to see the bio-luminescence. The southern part of Puerto Rico is beautiful with small well paved roads (no shoulders!)through desert scenery, and small Spanish-style towns that are spaced no more then a few miles apart. We did not see much traffic, the views of the oceans and farmland are awesome.
Ponce is a beautiful authentic spanish city - stay away the northeast / the San Juan area is a hell hole!

The center of the island is very, (VERY!) hilly and not in a good way, lots of small hills and quick gains and losses of elevation which can become demoralizing. PR-RT2 goes along the coast, but it is nearly impassable by bicycle between Ponce and Palomas - good to note.

For the most part we camped on beaches - which actually worked out very well. There are a lot of hurricane-ravened properties along the coast that worked as good squatting grounds. We had no problem with people, they were very friendly and all talked about relatives they had in New York city!