Just drive on the defensive and avoid driving at night. Bring a good map and go for it. From Juan Dolio you can head East all the way to Punta Cana. Check out the info pages on La Romana (one hour away) and Bavaro/Punta Cana at the left side bar of the travel index page. Note that it will take you three hours to get to Punta Cana.
Head West and visit the beach of Boca Chica, about half an hour away. Further west is Santo Domingo, the capital. If you want to visit Santo Domingo, head out early. Would recommend you park your car at a central point and then take a taxi to tour places to maximize your time. Driving in the city is complicated because of many one way streets and traffic jams. Better to hire a taxi.
There are gorgeous places out in the Southwest, but you would need to overnight as they are four to six hours drive away from Juan Dolio. And of course you could head north, but the North Coast (Puerto Plata) and North East coasts are another five hours away from Juan Dolio.
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