It is an interesting question. I don't have cast in stone opinion because there is more than 1 way to skin the cat, but personally always felt ... sort of nicer, not sure what is the right word, when driving on Sea to Sky and seeing these traffic signs with both English and Coast Salish names:
I think one has to ask the question: What does the name represent? It is human association with certain entity, be it mountain peak, printed book, or human being - so when this name is said, everyone knows what we are talking about. This is practical side; i.e "Garibaldi" or "Edmund Hillary" of "Vancouver Sun". In that respect changing "Garibaldi" back to "Nch'Kay" might not be good idea. In the other hand, names are also there to pay respect -- i.e. first ascent of mountain peak, or celebrate heritage -- i.e. native names. From that angle, "Elphinstone", although quite stylish indeed doesn't seem appropriate
This is maybe why I enjoyed dual traffic signs because I saw both practicality of modern times and heritage of the past in them.