Hostas grow like weeds pretty much anywhere in the Pacific Northwest......if you can keep the deer and slugs away from them :-) There shouldn't be any issues (other than those 2 already mentioned) growing them anywhere you like on Vancouver Island. FWIW, many hostas can be grown in full sun here without problems - we are far enough north that the sun even in summer is not very intense.

I echo Gardengal: Deer food. Be sure to get a place that is deer fenced.

It's just as Garden gal said Hosta's thrive here. The only problems are deer, slugs and unfortunately I have to add snails to that list. I think you could choose anywhere on the island for Hostas.
If you are interested in growing some of the more tender plants the closer to Victoria the better. They grow plants on the south end of the island that I can't grow here in Nanaimo.