Last time we went to Canada we added the $2.99 canada roaming (for $0.20 phone calls) and bought a Wind Mobile hotspot. Cost was CAD35 for 1 month, 10Gb HSDPA data. For CAD15 extra, you can roam on Tmobile + some ATT 3G in the US.
Wind only works in a few cities ( Windsor, London, GTA, Ottawa, Vancouver, Calgary, Edmonton) but is the best value if you want a cheap hotspot. Expect 1-3Mb/sec.