The Cangrejal River is within the Pico Bonito National Park, which is designated for tourism in its public use plan.
As a result, there is a network of trails that grant access to the park, most of them through the Cangrejal River Visitors Center, located about ¾ of a mile from the community of El Naranjo, between La Villa de Soledad Bed & Breakfast and the new Hotel Rio.
Access is via a 400 foot long suspension bridge, the type you see in Indiana Jones films. There is an entrance fee of $7.00 USA dollars per person.
Once on the opposite side of the river you will find two distinct trails. La Roca, which is a small loop that will take you about an hour to hike. El Mapache is the longer trail. This longer trail will take at least three hours round trip. This trail leads to the lovely El Bejuco waterfall. You can see this waterfall from the main road.
Although the trail is well marked, hire a guide. The trail is not especially difficult, but keep in mind that a good part of it is uphill. Mark your pace to avoid running out of breath right away! Sometimes you will find a guide at the visitors center. If this is the case, make sure you negotiate his fee. As a general rule, you should pay no more than $25 dollars for a round trip guided tour to the waterfall.
You can also hire hiking guide through any one of the three rafting outfitters in the Cangrejal river area. I suggest you hire a local company that belongs to young members of the community. The company is Cangrejal Tours. Some of the guides have received instruction and are actually quite good as bird watching guides.