You can drive there, it's right after Imbert, you'll a bunch of pesos-hungry guides for hire on the right side of road. Hire a guide to do all 27 falls, it's 450 pesos per person. Done it 5 times and will do it again on my next trip. It's gorgeous and a lot of fun. It's also getting well organized now. You don't need to book a tour in town, although they are very cheap if you don't have transportation to get there (a good 1.25 hrs from Sosua). Don't buy your tour in an All Inclusive but rather in places like El Tour and many others in Sosua/Caberete.