The Kansas-based church opposes gay rights and abortion, turning out for protests across the country with wide-ranging targets.
Chanting and holding signs at the funerals of service members, they said that the deaths are God's vengeance against a country for allowing gay rights.
They also plan to demonstrate at Edward's funeral for her support of gay marriage. For that, said a church leader, she deserved cancer.
"Then he gave her a whoring husband," said church member Shirley Phelps-Roper in an interview with NewsRadio 680 in North Carolina. "Don't you understand? You don't get to stomp your feet and flip off God and think it's going to go well for you."
The Mechanicals Theatre Group, which is producing the play at the Pico Playhouse, said they didn't anticipate the protesters coming to Los Angeles.
Artistic director Jacob Harvey can't say he is disappointed.
In a twist, the announcement from Westboro church has supporters of gay rights advocates buying out Sunday's performance.
"This is much more than we ever expected," Harvey said.
There remains a possibility that demonstrators will be no-shows at the play. There have been times that Westboro's protests have not materialized.
"I know that we have the people to support a larger louder message in response," Harvey said. "We are trying to turn lemons into lemonade they are sending a message of hate mongering and we are trying to combat that with a message of peace, love, equality and solidarity."