There is the data pack that folks have talked about.
I don't use my Cdn phone in the US much anymore after being stung with a $80 bill after our first 4 day trip to WDW where we just made a few quick calls and texts to each other - and it really was just a FEW to get in touch. We really didn't think it could have been that much.
We unlocked our cellphones and bought Tmobile prepaid SIM cards. We can get unlimited data and plenty of calls and texts for just $2 a day. Or if we don't want data, calls are just 10 cents a minute. Best of all, texting Canada is treated like a US text. Calling Canada is only 50 cents a minute.
Last summer I was in the US with a group of Cdn friends. I texted with them pretty much all day long (meet up here, I'm headed there, etc etc). Probably sent 50-100 texts. Don't know what their bills were like....Mine was a few dollars as it was 5 cents a text.
Also, about Mobile Magic - I tried to download it a couple of nights ago in Canada - and was denied saying I was in the wrong country
I'll have to wait until we get to WDW to download it!