After you pass Imbert, would say about 5 more kms, there is a small road community with signs of the Asociacion de Guias de Damajagua. You want to take a trip with one of those guys. I recommend you go very early, be there at around 8:30 am. The best way to do the trip is to hike up to the 27th fall and then make your way down. You have to be physically fit (just able to climb 6 floors without huffing and puffing), feel comfortable in water -- at least be able to do dog paddle. Bring good hiking shoes that can get wet -- even though I used Sperry Top Siders that were fine -- and clothes that can get wet. You will be jumping in and outside of the water. Would think a guide would charge about RD$400-RD$500 for the trip. At leisure, it should take you about 5 hours. They may suggest going only up to the 7th hole and then back, but it's best to hike and then jump and slide down.
As Chris said, since it has been raining a lot, some falls may be dangerous. But that is why you go with one of the guides that will know which ones need to be avoided.