Well, if you want to be "practical" as you suggest, methinks a driver's license or state-issued form of ID from any state would suffice. Just like any prudent individual would carry before this new Arizona law. A DL is a state-issued form of personal identification by which one has already proven their date of birth and place of origin to authorities in (albeit) another state. Though admittedly I think there are a handful states who might be a bit fuzzy in their criteria for issuing licenses which Arizona could in theory question ( if one wants to assume the worst ). But this disparity reflects the diverse powers of a federal republic which allows States to set their own rules within the bounds of the Constitution. Foreign nationals should behave/respond as they always do in a foreign country. You have your own national/state issued driver's license and you might be well advised to keep your passport on your person in case of an emergency. Non-citizens who are visiting on a VISA etc. would want to have those relevant documents as well ( not just for Arizona, but any contingent situation they might unexpectedly encounter ).

In short, I don't see any issues for any individual, citizen, alien, or legal immigrant visiting Arizona, nor would I anticipate heightened/deliberate enforcement. It's all contingent upon other factors setting in motion what ever the vagaraties of the new law are.

Barry