Can't say how big F1 is in Vancouver, it's certainly huge in my circle of friends though. I am very aware that Mtl is unlikely to give up there race though, so I'm going there instead for the 2011 race. When I retire in a few years one of the first things I'm doing is following the F1 circuit for a season.
The Vancouver Indy was the largest attended race on the old Indy circuit and drew more people then quite a few of the F1 races do today. F1 is a completely different league though so it's hard to say how we'd fare. We also don't have a shot at a race with Mtl holding one, and they won't give it up. The best we could hope for is if they need to close their track for repairs and need to sit out a year, but even then there are enough cities ready to leap at that opportunity.
We'd have better luck holding a major Bike Race across the province ala Tour de France. Wouldn't be as big of a draw but would draw media attention to the whole province.