Yep. I only recall seeing them in Oregon though - not California or Washington (Washington has warning signs for everything else though - including no warning signs - https://i.imgur.com/T868pkg.jpg )
Washington has them, it was one of the first things I noticed when I got the motorcycle out for a coastal ride when I first moved here 20-some years ago. Couldn't tell you exactly where, but they're there and within an easy Saturday ride from Redmond. (Westport or Grayland, maybe?)
It's been a few years, but I don't recall them in Kalaloch, La Push, or Ozette... but then that was '09. The picture of the no warning signs warning was on the road to Ozette. It does appear that they are there now, so it might have been me misremembering ( https://goo.gl/maps/ofY3GGHDnuG5GWaZ6 )
They've changed them, though. They used to have a person climbing a hill as the wave comes chasing after them. Can't find a good example on image search. I found the old signs to be morbidly amusing. Like my spindly little legs are going to save me.
