Dionne Warwick will attend a Harlem Town Hall along with doctors, patients, activists, and a few show business friends (Rosie Perez, Michael Kenneth Williams from “The Wire,” Sheryl Lee Ralph from “Dreamgirls”) and join in a discussion of AIDS, its effects on urban communities, and steps being taken to find treatments and an eventual cure. Ms. Warwick has been involved in AIDS awareness and activism since the 1980s, when her valet started being diagnosed with the disease.