I'm open to be corrected here but...
OP mentioned they have iPhones. If they're 3G models or newer, I thought they would work on TELUS' new HSPA network.

I'm pulling the band specs for the iPhone 3G from Wikipedia.
"In addition to previous: Assisted GPS, Tri-band UMTS/HSDPA (850, 1900, 2100 MHz)"
TELUS new network uses 850MHz and 1900MHz (based on this thread, post #8).

However, as originally mentioned, I initially didn't think TELUS did data (plans) on prepay. The following link says sim card phones on the PrePay network is subject to pay per use fees which are likely pretty pricey.
http://www.telusmobility.com/en/BC/p...?eVar6=link#C1

But my buddy says he's pretty sure they do that $20 250MB data plan on Pay and Talk now as I mentioned in the previous post (and that they probably just haven't updated the Pay and Talk FAQ's website). This data add-on links from the Pay and Talk plans page.

If this iPhone solution actually works, you might want to consider TELUS since you're staying in BC. TELUS is the incumbent provider in BC and likely has better HSPA+ coverage from their new network than Rogers/Fido. In the larger urban centres, it's probably a wash. On the other hand, you can likely fall back to a larger Rogers GSM coverage area with any of your GSM phones but that likely won't help much with you data needs.

http://www.telusmobility.com/en/BC/h...da3gmaps.shtml
http://www.rogers.com/web/content/wi...909-_-coverage