If it's a US iPhone 4, I'm pretty sure it'd work on the TELUS network since it's one of the phones TELUS offers. (The quirk with AN*G-BNE's iPhone was that it seemed to be a different version, lacking a band.)

If you're only going for a week, Rogers/Fido might be a more economical solution since they have a weekly data plan whereas it seems TELUS only has a monthly one.

BTW: AN*G-BNE's... good info in your follow-up. ^. Personally, I like to do things myself but my buddy and I have similarly run into various issues when trying to register/config phones in the States as well. Find it's just simpler to just have everything done in a store.