There is an airfare sale down to $214 round trip between Los Angeles LAX and Vancouver YVR and $229 between San Francisco SFO and Vancouver. These fares are available some dates in June, July and August, then most dates through March 2017. Lowest fares are US to Canada one-way segments priced from $99 to $117. Air Canada and United offer nonstop service. American flights route through Phoenix PHX and many of the low fares have long layovers from 5 to 12 hours in PHX.
United Airlines San Francisco – Vancouver YVR Google Flights search
$229 round trip Wednesday July 6 – Wednesday July 13
American Airlines Los Angeles LAX – Phoenix PHX – Vancouver YVR
$233.36 round trip Tuesday July 12 – Sunday July 17
Loyalty Traveler – Hotel Promotions Guide May 2016.