Please don't turn back towards the shore once you leave Waimea Canyon!!!! You'll miss one of the most amazing views of the Kalalau Valley and the Na Pali cliffs. If you continue on Hwy 550 past the canyon lookout and go as far as you can, you'll reach the Pu'u O Kila Lookout. The views from here are breathtaking.
Kalaulau Beach and Valley can only be reached by foot from the Kalalau Trail or by privately chartered boat (which, as you may guess can cost you your first born). So for those of us who don't feel like hiking for a week, or don't want to give up our first born, this may be the only way you can see such an awesome sight. You could also take a helicopter tour or a boat tour, but this is the way to go if you are on a budget.
When you go, be sure to go all the way to the end of the road--which is about 19 miles from the start of Hwy 550. Don't stop at the Kalalau Valley Lookout as the views are not quite as spectacular.