Ha ha, as a fellow hearing autistic, with a post count above 1000, I hardly think you're "infiltrating"--hearing people can join and participate too! (jillio for example is also hearing)
Yes, I totally agree with you about signing. It's a lot of fun to learn because of its visual/kinesthetic nature. And I have a mild auditory processing disorder with my autism as well... XD
I guess maybe you didn't expect to find another one of us here? :P
Now, I can sort of answer your question, since I've had experience (and did become fluent in ASL)... Write it down! Many deaf people seem to appreciate it when you're not afraid to write it down, since deaf people tend to also be literate. Even if you can't sign, carrying out the conversation in a written or typed form can do wonders for mutual understanding.
Hope this helps, and if you need someone to talk to who's been there, feel free to send me a message! I can try to help you with signing questions as well. 
