An easy side trip from the Hilo area, you have two options: a short trek to 'Akaka falls and a longer loop that will let you see another waterfall.
We did the short loop and Akaka falls is certainly a beautiful waterfall...very tall. There are some smaller ones before you get to it and some very interesting vegetation.
As other reviews have said, there are restrooms there. On the road leading to the highway, stop at the coffee shop/gallery for Tropical Dreams icecream and some nice prints/souvenirs as well.