Just back from a 4 weeks stay in Nanning and there´s busline 7 going from Nanning Dong to downtown (last stop is the old train station).
You need about 1h, last bus leaves at midnight for downtown and vice versa.
Line 7 ends at Suzhou Lu, just close to the old train station.
Many thanks for your inspirational PM. We're actually bringing our entire Nanning crew to Shanghai next week (which spares us of the need to go down there, and is good for them...they will get to meet our clients).
Your observation about the lack of an expat job market (apart from teaching English) is spot on. Foreigners in Nanning teach English, are retired, or work for German companies. (Of course this is generalization, but it's pretty spot on.)