I don't recall that the Ski to Sky Hwy had that good of a shoulder or bike lane. It's a pretty narrow and winding road, so I wouldn't recommend that.
I remember seeing a lot of folks on cruiser bikes around town and some mixed use trails, so if you're into chilled biking experiences I think that's a for sure thing. I just don't think there's a ton of hardcore, Tour de France stuff out there.
Plus, you gotta think about the bears. I hate to say it, but the bears really can be anywhere and everywhere. We hear about them cruising around the golf courses and such. I don't know if they're a problem on the mt bike trails, but encounters have increased in town. Just google "whistler bear attacks". I'm not trying to scare you, but I sure wouldn't be engaging the chase reaction up there.