Elk River Falls are located about a 5 mile drive from the little airstrip (Pvt) in the town of Elk River, ID. To get there, I recommend wandering around town looking lost. One of the locals will surely offer you a ride in no time.
Viewing all three levels of the falls requires a substantial hike that is mostly straight up and straight down. If you're out of shape, you'll know it as soon as you start the hike back up out of the canyon.
Right next to the airport is the Elk Butte Log Inn where our new friend Travis was cooking their famous Burgers (I highly recommend the Travis Burger). Travis also was quick to arrange our ride to the trailhead at the falls. If you're ever in the area, stop in for a bite, the food is great.
Update : On a visit in '05 we found that the Log Inn had changed ownership and Travis was no longer there. If you're out there Travis, drop me an e-mail. We still owe you a plane ride.