If you don’t have a rental car, not to worry. Book your tours with the local cooperative Guanaventuras. Tours are run by a local guide who will take you to off the beaten path as well as well-known sights in this region.
If you have a car–which is the best way to explore this region–you can easily reach the national parks or go to Bahia de Las Aguilas. Just look out for obstacles on the road, including cows.
There is a public guagua (bus) that travels from Barahona city down the coastal highway all the way to Pedernales–if you’re up for a really long, dull ride for four to five hours. If you’re just going from one small town to another, it should be fine. Just wait on the side of the road and hope one turns up every half hour.