How far is it to Mt. Huashan from Nanning? I will be in NN in May.

By road, there is about 2400km between the Mt. Hua and NN.
The mountain is in Shaanxi Province in northwest part of China.
If you intend to climb, you can fly to Xian first and then use the local Tourism Bus Line 1 to reach the mountain directly. (the tourism bus is in front of the railway station square.)