Thanks and welcome to the Great American RoadTrip Forum! February going up the coast could be beautiful -- in fact, the weather is usually much nicer (in terms of clear skies) in February than in the summer months (which for us would be in July and August) -- However, given the options, I would suggest you spend five days or so exploring northern Arizona & southern Utah -- here's a great route and then fly direct from Phoenix to Vancouver. It really doesn't make much sense to drive to Denver and then fly -- you could hit some serious winter weather in the Colorado Rockies and miss your connections to Vancouver.
Mark