yes you can you just show them under" all other fowl class" its all good you can even show mutt birds under that class my kids do it at are county fair all the time and i did it when i was a teenager now if its a state fair that might be differen't .
i entered them in all other fowl my first year, they called me and told me they cannot be shown at all under any class, the APA dont recognize them and you can only show APA recognized fowl, maybe thats just the fair i showed at..
It is up to the poultry superintendent. at our fair that was me. there were EEs, sex links and even some "banties " of very mixed origins. many of which showed up the day of the fair with no registration. yay fun for me