Assuming you have already been to Santo Domingo...
Make a first stop in Caribbean Sun (Playa Caribe - Embassy Beach) for great wave riding and good food. Go early in the morning through noon.
Next beach town is Guayacanes worth eating there. Deli Swiss has its own beach where you can go swimming -- also El Ensueño Restaurant is popular.
Next is Juan Dolio -- in place there is Aura. Worth dropping in at least for drinks. One of my favorites is the Cucina de la Nona (or something like that -- an Italian grandmother cooks) -- located on the Calle Principal on the way east of Capella Beach Resort.
Spend three nights in Bayahibe. Avoid being there on a weekend, when the crowds show up.
Stock up on food stuffs in La Romana's Jumbo supermarket.
La Romana is a good place for shopping around. Just tour up and down the streets. Lots of good restaurants.
Stay at Bocayate on Calle Dominicus in Bayahibe that is new and am told has kitchen. You can then prepare your own breakfast. There is a cheap and very good cafe -- cafe de la cubana, right on the corner of the beach where the boats dock. Good capuccino, milk shakes, great prices.
Visit Dominicus public beach (between Viva Dominicus and Iberostar).
Book a boat trip for snorkeling in Bayahibe. Visit the new big ball reefs. Take a trip to Saona island and make a stopover in Palmilla. Snorkel and sea sea stars in their natural habitat.
Head out to Boca de Yuma. Visit Ponce de Leon house in San Rafael de Yuma -- about two-three kms inland. Overnight in Boca de Yuma for two nights. Take the boat trip up the rio duey, to see still preserved fauna and flora. Take the same boat trip to the little beach in front. Bring your lunch.
Detour to visit the Basilica La Altagracia. Did you know the DR has the first two Virgin Marys in the Americas -- Las Mercedes (in La Vega) and La Altagracia in Higuey. Pope John Paul II said mass there.