Thanks for the responses. I've found an AT&T store right when I cross into Detroit. I'm contemplating making my first trip to Bloomington and either Haubstadt or North Vernon on the 19th and 20th.

For me to use my phone in the US, I pay $6.00 /mb. (I would have spent $310 today alone!) Calling home is $1.45 a minute, and text to Canada are $0.75 each. It's nothing out of the ordinary for people to accidentally run up $500 phone bills from roaming.

I'll be able to donate all these savings to some new racing T-shirts and hopefully help out some racers!