AEPhi does not have an official hand sign.
I think that we would sign the letters "A-E-P-H-I", because if you tried to spell out "A-L-P-H-A-E-P-S-I-L-O-N-P-H-I" during formal recruitment, the party would be over by the time you were done signing.
The issue never came up, as we never had a deaf PNM come through while I was an active or a rho chi.
But now you've got me thinking, because my mother was partially deaf. Not only do you have to converse with a deaf PNM during recruitment, you also have to bring her through new member education, and you have to bring her through initiation when she cannot hear what is spoken. Many deaf people can lip-read (heck, I have perfect hearing and I sometimes rely on lip-reading if I'm in a noisy room) but you still miss things even when lip-reading. I wonder if a chapter will call upon a national volunteer, who is hearing and who knows ASL, to sign during ritual?