I have been to Beijing, WeiHai, Shanghai, Changsha, Guangzhou, Qingzhao, ShenZhen, Haikou, Sanya and now live in Hainan Dongfang.
The only city I've been to, where they seem to speak clean pure Mandarin is Beijing. My wife is from Changsha an she destroys Mandarin, No ch or sh sounds to start words, she tells everyone she is from Cangsa, leaves off g's at ends of words, add g's where they don't belong any Hu is Fu to her, and when she talks she mixes Mandarin with Changsha Hua. My problem is I'm picking up these bad habits'
When we were in Beijing people told me they could understand me, better than my wife.