Broadway turned out en masse for the opening of “The Road to Mecca” by Athol Fugard, who will soon turn 80.And the play marks Rosemary Harris’ 60th year as a leading lady on the Rialto. The 85-year-old thesp said the role of Miss Helen represented a rare leading part for an actress of her experience. “Even Shakespeare only wrote so many parts for women in their 70s, and most of those are mad queens,” Harris noted. After the preem at the American Airlines Theater, co-stars Carla Gugino and Jim Dale joined with Harris next door at B.B. King’s for chicory Roquefort salad, rigatoni and sponsored cocktails like the Miss Helen’s Artificial Sweetener: vodka mixed with orange juice.