Here’s an article I read about Spring Awakening on Broadway, which includes American Sign Language and spoken English.
The character Moritz is played by two actors. Alex Boniello, who is hearing, sings and speaks the lines. Daniel Durant, who is deaf, signs all the words. The two actors work together to portray one character. It gives two different sides to the character and his story. This article has an interview with Alex and Daniel explaining their relationship and how they work together.
Including ASL and deaf actors is what has made this revival so successful. Making such a groundbreaking show accessible to deaf audiences and actors has really changed Broadway.