The Didi driver will want to call you. They do this reliably. This presents you with two problems: (1) Roaming assuming you don't have a Chinese SIM and (2) Language assuming you don't speak Chinese.

The app does translate for you from English to Chinese and has some stock phrases (I am at the GPS location) but they will still try to call you and you'll have the above two problems. I live here and always have a Chinese speaker nearby when I use Didi. Last night at Shenzhen Airport there's a specific place for e-share cars (ie Didi) and sure enough the driver called even though I messaged him. I always look for teenagers in this situation: they tend to speak English and understand the conversation I need them to have.

I'd get a taxi if I were you.