He isn't trying to be rude by falling back into speaking, it's just that he still doesn't know enough sign to hold a conversation at the moment. There hadn't been enough time between starting lessons and being deployed for him to know more than perhaps a handful of phrases at this point. That and his other hand was a little full with the waterskin.

"Yeah... is there something giving you trouble?" As he asks he silently offers the waterskin, brows quirking up in curiosity.