Angels in America makes no effort to be coy about sex. The characters speak about it openly, and they aren't afraid to crack a sexual joke or two. The play also shows sex on stage with Louis and an anonymous man in the park, and every time Prior feels the angel coming, he gets an erection. There's also nudity, though it isn't sexual in nature.
We should note that some critics have accused the script of being pornography, and actors performing the play have even been threatened with jail time. This really doesn't seem fair, however. The play's frank sexual references definitely make it fit for mature audiences, but so do its sweeping themes, beautiful language, and complex analysis of the human condition.