“Dark Angel” costars Jessica Alba, 20, and Michael Weatherly, 32, are engaged to be married, her publicist said Tuesday. No date has been announced. On the Fox sci-fi series, Alba plays Max, a genetically augmented human prototype, and Weatherly plays a cyber journalist, Logan. Two weeks ago, at the American Latino Media Awards, Alba, whose first movie was 1994’s “Camp Nowhere,” was honored as a breakthrough performer.