Hello Nick,
The surf in downtown Santo Domingo is usually better October - April, unless a tropical storm passes to the south of the city. Guibia is the only break in the city. The reef and sand-breaking waves are slow but consistent, and can be ridden 2-6 feet. About 50 km. to the east of the city near Juan Dolio is another popular spot called Embassy Beach (next to the Embassy Hotel). It breaks in a cove with reefs on each side. The waves are cleaner that Guibia and good for beginners, but the current can be quite strong.
La Boya near a sugar mill just west of Boca Chica is an excellent right when it's up. With offshore breezes, long 5'-10' swells, it can resemble Mailbu, California without the crowds. There's another shallow break on the other side of the channel. Watch out for sea urchins.
Visit in the winter and you won't be disappointed. And try the north coast too. It has more breaks, consistency, and larger swells.
Western Puerto Rico is certainly worth a visit--I lived there for six years--with the best waves in the Caribbean. The 12-hour ferry ride runs nightly between Santo Domingo and Mayaguez, PR. Most surfers live 15 miles north of Mayaguez in Rincon. You can also fly Santo Domingo-San Juan, PR and then go by road or small plane the 85 miles to the west coast. Rincon is a winter spot, with flat spells lasting from May to September. North of Rincon, Aguadilla and Isabella break all summer.