can't say about other states, but Alberta allows you to drive on IDP / you county's DL for 3 months for Permanents residents and 1 year on IDP only for temporary residents after they enter Alberta. E.g. if you were in Ontario for initial 5 months and did not secure a DL, and then enter AB, you will be allowed to drive for 3 months.
This rule expires at the end of 1 year of entry into Canada...
this was the rule back in 2007. Not sure if thing've changed now...