If you really want to learn authentic Mandarin, please go to the cultural centre --- Beijing City. If you go to Shanghai, Hebei, Shandong, or Liaoning, it would be just like you go to Germany to learn French, or you go to France to learn Italian, can you understand? If you wanna learn Wunese (吴语), Shanghai & Suzhou will be the best places for you. And Shandong dialect would be even too difficult & strange for our Chinese. The dialects of Heibei & Dalian aren't standard Mandarin, either.

Dalian or Qingdao would be a good choice, both matching your criteria and I can really recommend them.

well the best choice i should say is Dalian which is located in Liaoning province. it's a coastal city, very safe --you know, a lot of celebrity living there. Also it enjoy vast education resource, Dalian Ligong, Dalian Haishi, Dongbei Caijing, the are in of great famous. this city have the most beautiful and clean park in china, which is Laohutan Park, and its pleasant coastline accompany the bluesky and white cloud, in the good day you could see another country over the Yellow sea-Korea when you are walking on the beath. Women Ranger Police are unique in china and Dangdang bus has the oldest history of the nation, which are still sever for the citizen. The last but not least is the delicious food, it collect Chinese, Japanese, Korean food together which will enable you take a try in one travel annnnnd all the food are very cheap and substantial, so I can make a bet Dalian won't let you down!!!

Tianjing isthe best city for you .It is close to Beijing and sea.Besides,It is a city with universities, safe, beautiful, clean and modern.

You want to speak standard chinese mandarin? I suggest Harbin. They speak very standard and their local dialect (dong bei hua) is not far off from mandarin. Ask anybody from harbin and they will tell you how proud they are of their "standard chinese speaking" furthermore it is cheaper to learn in harbin then in other cities. (rent, food, tuition etc). many korean and japanese people go to harbin to study for the HSK. there are two main universities (哈工大）(黑龙江大学）both have good chinese teaching programs. I go to a private chinese school in harbin as I'm also an english teacher and don't have time for regular school. I have three different chinese classes three times a week. they are all one on one and my teachers (three different teachers) can't speak english which forces me to use mandarin. furthermore, in this city you need mandarin and will speak it everyday. from the doctor's office to buying food. The only drawback to harbin is its weather. It gets pretty cold here during the winter. But because I'm a Canadian I use to it. if interested in harbin leave me a message I would be glad to help you out. Good Luck.