Oh yeah, any type of dogs can learn ASL and hand signals. I have a dog that is English Springer Spanial and a Shetland Sheepdog and they know my asl signs pretty good. I trained them pretty young and they were great. Dogs are more likely to response well with hands signals just like ASL. You should watch a man name "Cesar Milan the dog whisper" show and he help train people and dogs to understand each other better. He is wonderful!
"The rain may be falling hard outside,
But your smile makes it all alright.
I'm so glad that you're my friend.
I know our friendship will never end."
-- Robert Alan