You can configure iTunes to download into MP3 format as opposed to ACC format. However, the other posters are correct that this is actually a protected MP3 format and will not be transferable to the pocket dish.
The way around this is to burn to CD and reimport. Then you have regular MP3 format and you will be fine. I do this quite a bit to move downloaded music into my mixing software. It is a little bit of a pain, but really does not take that much time to do.