HIGH ROMANCE: When Rep. Christopher Cox (R-Newport Beach) worked at the Reagan White House, it wasn't exactly all business. Cox, 39, also met Rebecca Range, 37, now a Continental Airlines executive, whom he will marry Aug. 29 in Orange. She was also on Reagan's staff. It is Cox's first marriage, her second. . . . Cox serves on a committee that oversees airline legislation, but he doesn't see a conflict: "We know each other well enough not to talk to each other about those things."