Spent 6 days in Puerto Rico over Spring Break. The casinos are better than the ones in Florida but that is not saying much. Kenny is right, the pit bosses are ridiculous and the dealers are quite unprofessional. Two dealers I had both accidentally flipped over cards on a few occasions and also I did not know this, but apparently if after the deck is reshuffled a player is given the option of putting a red or blue card in the deck and she forgot to do that. The place I played at, the dealer got her second card before everyone began to hit or stand, but I only played in that one place so don't know if the rest of the island is like that.
KU, do you want to see touristy San Juan or the real Puerto Rico? Either way you definitely have to see El Morro and the other forts in Old San Juan, the El Yunque Rain Forest (take the Britton Hill trail if you're not in superb shape as you will still have beautiful views without the work of actually summitting the highest point), the beaches around Rincon, the Arecibo telescope, and the Rio Camuy cave system.
Keep in mind that once you are off the beaten path in PR, you are off the beaten path. Outside the big cities, you will have a hard time finding anyone who can speak more than a few phrases in English. Also, the roads and drivers there are absolutely horrible. Red lights are constantly run, cars constantly cut you off, people pull out soon as one lane is free on a turn and stop traffic to make a turn on to the main road, etc. If you're renting a car, the driving will get on your nerves quick, especially if you drive around as much as I did.
Other things you should see if you have enough time: the bioluminescent bay in Fajardo (the tour is steep, $40 or $45, but if the boats aren't full, you can bargain), downtown Ponce and the HUGE cross overlooking the city, as well as Las Tibes right outside of Ponce. I didn't go to Cabo Rojo, Vieques or Culebra, but I heard that those places are great and quite touristy.
Places to stay out of are Mayaguez (we were specifically told that they do not like non-locals there and one of the hobbies is to drive around looking for foreigners to beat up after a night of drinking), the Ruta Panoramica (nice for 30 minutes and some good views but the shit gets old quick), Guayama and Adjuntas (the traffic and roads here are particularly atrocious), and Humacao.
Hope this mini-guide was of some help you you KU, and if you have any questions feel free to ask and I'll answer the best I can. Have a good time there man.