B.C. has saltwater fishing opportunites year round. For Coho and Chinook (Silvers and Kings), that's primarily a summer season. We had good luck limiting out in mid-June in Bamfield. Nice Chinook, up to about 30 lbs. That trip was on the early side.
July, August and September are usually more reliable, and the Coho will be larger the later you get in the season. For the most part, the season will stay strong until a couple of large rain storms hit (Mid to Late Septemer) and the fish hit the rivers.
The west side of Vancouver Island is great (Bamfield, Tofino, Ucluelet). This is ocean fishing and you need to be comfortable in swells and heading off-shore.
I haven't spent much time fishing the inside areas east of Vancouver Island. Others on the site can give you better insight for these areas.
The Queen Charlotte's are great. Excellent fishing for Salmon, Halibut, Etc. Beautiful scenery. Very remote, so more of a fly-into kind of place, but well worth it.