RIU Resorts. When you get there it's a "compound" and by going all inclusive, you can visit any of the other RIU resorts within the compound. You get a wrist bracelet to wear that shows you are an all-inclusive guest. There are also extras you can arrange, such as parasailing, swimming with dolphins, excursions, etc, but there was plenty to do within the resort complex without paying extra.
Also, no matter where you go in the DR
1) Always make your arrangements through the hotel or a travel agent for excursions. There are guys that park a boat off the beach and jump ashore and try to convince you to book something through them. Not good deals when you factor in they may not be reputiable.
2) Do not rent a car, arrange transportation to and from the airport. Any excursions will come and pick you up at the resort you stay at. There is no way an American can navigate those roads safely. You want a car cab or van and you will have to specify that or they'll come get you on a motorbike.
3) Pack your own asprin, sunblock, aloe vera, etc. American conveniences are really pricey.
4) The weather is really comfortable, but always wear sunblock as the sun is much more direct.
5) Don't be shocked when you see folks go topless at the beaches.
6) Don't gamble. Gambling is not regulated as it is in the US.
7) Don't drink the tap water. Make sure the bottled water is sealed.