You can on both iOS and Android. I can't speak for iOS but as far as Android goes, you should have your printer's app installed to be able to "share" the project from PS Touch. (In the project selection user interface, you would browse to the project you want to export for printing, tap the export icon (5th icon from the upper right) > Share > tap the project and select a format (like JPEG) > select your printer app.)
Take note some apps (maybe all) act a little wonky no matter what you do. For example, Epson's iPrint app will cut off the sides for no darned reason, even if you give exact dimensions for a given print size. You might be better off just exporting the project to a cloud storage service and then printing it out via desktop later.