Info from Internet:
Two ways from Nanning to Detian:
Direct bus from Nanning Langdong Coach Station (南宁琅东汽车站) to Detian, depart at 0830 and arrive at 1300, about rmb50.

Take a bus from Nanning North Passenger Transportation Center (南宁北大客运站) to Daxin County (大新县); transfer to the bus from Daxin to Xialei(下雷) and alight at Shuolong Village (硕龙镇), then hire a motor taxi to Detian (rmb5 and 15 minutes)
Nanning-Daxin: 0610-1900, every 20-30 minutes; Ticket price is about rmb38-47; 2.5 hours.
Daxin-Shuolong Village: RMB10, an hour.