Have also stayed at the Caribe Hilton and it was a very nice property. It is on the pricey side and does not have a casino though. I just happened at the time to get a deal.
Have heard good reviews about the Wyndham El San Juan Hotel and Casino, quite pricey. Condado Plaza Hotel and Casino, that Penny mentioned was a little less pricey when I searched a while back, and had good reviews.
As Sonny said about using Priceline, if I could get the Caribe Hilton for anywhere close to $100. I would rather stay there and take a short taxi ride to the Casinos. Because it has such great outdoor amenities, and is more secluded.
If a resort type property is not the priority and being close to the cruise terminal is a priority. There is the Sheraton Old San Juan that has a casino, and is just across from pier #4. I don't know the price range.
Personally, I would opt for the Hilton or the Condado and Isla Verde Hotels.