$25 2GB Data Add-On - OK for Prepaid?

[wireless]

I have an unlocked ATT iPhone 3GS I want to use when visiting Canada and enable personal hotspot so I have Internet access on the phone and on my laptop for work. I usually buy the $2/day pre-paid plan - can I purchase any of the data passes or data add-ons (specifically the 500MB or 2GB...

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