Yep. You will only find it on rocky coasts...It seems in its native range there are inland forms, but so far these are just along the shore. It would be interesting to see the true extent of their range. My guess is they dont get too far out the Olympic peninsula and not as far north as the 49th. I will have a look for some next time I go to Tofino.

I'll be on a trip to the West Coast this August, so I was thinking that I might have a chance of meeting this and other western species. I'll be in the coastal region and on the Island for sure, but, this seems to be too rare to find without a lengthy search. So I guess I'm out of luck :-(

It is not too rare actually. Just target these upper splash zone pools. Or have a beach fire at night in a rocky cove. They will find you.
The only other larvae you are liable to see in those pools is Culiseta incidens, which are easily told apart from these by their long thin siphons. Aedes types have stubby fat ones.

I'll keep those distinguishing characteristics in mind when I go. Don't know what I may actually encounter, but that's all part of the adventure.