I think your answer misses the point of the question. Learning ASL can be done after the surgery if she lost her voice. The question was what can be done now before the surgery. The kind of things which, if it comes to the worst and she loses her voice, cannot be done after.
I wouldn't discount the value of having some rudimentary signs to communicate immediately after surgery. It seems odd to me to focus on some dream of a perfect TTS synthesis if these more basic needs are not addressed first.
If you've ever had a mouth injury that inhibits talking, or been in a foreign environment where your speech is totally useless, it can be very stressful to be unable to communicate. I think the couple should consider learning some of the basics ahead of time, so that communication is possible without typing or any other apparatus.
Considering post-surgery recovery window, I'd want to be able to express very basic things like:
I am comfortable
I am in pain
I am hungry
I am nauseated
I need to urinate/defecate
I want to rest
I love you
When will you return
etc. I might suggest trying to boil down one or two inside-joke kinds of phrases as well, to be able to lift each others spirits in private or intimate way.
If it must, but it isn't as smooth as conversation can be. sign language is a real language, and you can have real conversation, with all the pros and cons of real conversation.
