I have a 9 hour layover at Bayun airport. Is that enough time to visit the city and go back?

Yes, local subway line 3 leads to the airport directly!

Well, hurry up and you can spare some time for sightseeing in the city. You may choose to visit the local White Cloud Mountain by metro or take shuttle bus line 5 to Haizhu Plaza and then walk along Yanjiang Road to enjoy the Pearl River and then walk to Beijing Road for fun and possible shopping. Control your time well and get back using public transportation. If time is tight, take a taxi to return the airport after visiting!