Certainly that's a viable choice, assuming:

You live close enough to an AM radio station and/or have the willingness and knowledge required to throw up a fairly long antenna. It's not rocket science by any stretch of the imagine, but it's definitely not something you'd want to try to figure out in the middle of an actual emergency. Anyone contemplating this technique should try it out well ahead of time; though this is more or less true of all our equipment. The plus side is that you'll have uninterrupted radio reception so long as the station is transmitting. I have a crystal radio in my living room that has been 'running' almost continuously for the last three years.

Finding a GOOD commercially produced crystal radio can be tough, though there are plenty of so-so receivers out there that will operate reasonably well if given a strong enough signal to work with. I believe Radio Shack still sells such a receiver. Another viable option is to roll your own. They're not particularly difficult to build and you'll learn a great deal about radio in the process.