THE city’s unofficial motto, “Keep Austin Weird,” blares from bumper stickers on BMWs and jalopies alike, on T-shirts worn by joggers along Lady Bird Lake and in the windows of independently owned shops and restaurants. It’s an exhortation for a city that clings to eccentricity, even in the face of rapid development — downtown Austin, for one, is being transformed with a fleet of high-rise condos and a W Hotel, scheduled to open late next year. But this funky college town, known for its liberal leanings and rich music scene, has little to worry about — at least as long as its openhearted citizens, with their colorful bungalows and tattoos, do their part to keep the city endearingly odd. As one local put it: “As long as Austinites keep decorating their bodies and cars, we’re going to be fine.”