What Mandarin do I actually need to get around?

Short answer

You can manage on about twenty phrases and a translation app. Learn the numbers first, then how to ask what something costs, how to say what you do not eat, and how to ask for help.

The ones you will use every day

EnglishMandarinRoughly
Hello你好nee-how
Thank you谢谢shyeh-shyeh
How much?多少钱?dwor-shaow chyen
Too expensive太贵了tie gway luh
I don’t understand我不懂wor boo dong
I don’t speak Chinese我不会说中文wor boo hway shwor jong-wen
Where is the toilet?洗手间在哪里?shee-show-jyen dzai na-lee
This one这个jay-guh
No thank you不用了,谢谢boo yong luh, shyeh-shyeh

Food, which is where it gets personal

EnglishMandarin
I don’t eat pork我不吃猪肉
No meat不要肉
Not spicy不要辣
A little spicy微辣
Is there halal food?有清真食品吗?

Halal food is easier to find than people expect. Look for 清真 on a sign; there are Muslim-run restaurants near most large universities and through parts of Futian.

When something goes wrong

EnglishMandarin
Help救命
Please call the police请报警
Please call an ambulance请叫救护车
I want to contact my consulate我要联系我的领事馆
Please find someone who speaks English请找会说英语的人

Screenshot these five into your photo album so you can reach them without a network. They are also on the emergency page, set large enough to hold up to a stranger.

Tones, briefly

Mandarin has four tones and you will get them wrong for a long time. Say the phrase anyway, because context does most of the work and people are generous with someone who is trying.

Also asked

Will people speak English?

Often in universities, international companies and large hotels. Much less in the market, the clinic, the police station and the noodle shop, and those are the places where a few phrases save you.

Which translation app works in China?

Pleco for looking up a character you are staring at, and Baidu Translate or the translation built into WeChat for a conversation. Google Translate does not work on Chinese networks.