Getting around Shanghai and Hong Kong was super exciting. I had a lot of great eating, and a lot of great yelling in Mandarin, and just generally a pretty great time. For the most part I ate at vegetarian restaurants, where the only concern was whether or not it contained egg or dairy, and this was usually pretty easy to suss out.
On one occasion I had cause to eat at a meat-serving restaurant, where nobody spoke English. Despite the wide choice of vego restaurants to visit, with their english-subtitled menus where pointing could take place, this meal did highlight how convenient it was that I speak Mandarin, and I was comforted when our server used the magic word (素) to describe what she was recommending.
Hong Kong was a little English-speaking, though I did have to use my terrible canto skills to get by at some points. After two weeks adventuring through Shanghai and Hong Kong having to speak either Mandarin or Cantonese every day, I don't know how someone who didn't speak any Mandarin or Cantonese would fare. I was definitely glad I can read Chinese characters, because often there was no English to be had. This also made reading train maps in Shanghai a lot easier, though there were sometimes subtitles there, too.
Speaking of the train maps: the trains in Shanghai and in Hong Kong are pretty great. Easy to use and easy to get around, and cheap. If I did it again I'd seriously consider a top up card for Shanghai, due to the frequency with which the ticket machines broke or were unavailable. The stations themselves are massive, and many of the entrances are not great for people with mobility issues, or with sight issues.
The only food backup I really relied on was the corn on the cob you can get from stalls as you wander by. I had seen stalls selling you tiao/yao chao guai one morning, on my way to a temple; however on my return they had packed up and I was so disappointed.
Using Happy Cow was mostly fine, though a few of the details were out of date. I didn't really do much research beforehand into what restaurants would be good, I kind of just went for it. I had one bad restaurant experience, at the Jade Buddha restaurant, where despite the restaurant only being half full we were unable to be seated, and the wait staff refused to even catch my eye, so we left. Also I can confirm that the restaurant at Jing'an Temple has indeed closed, much to our chagrin.
Please note that everyone smokes, and most places allow smoking indoors. And many places are filled with stairs.
A summary of my Shanghai and Hong Kong posts:
i: godly vegetarian [功德林素菜馆], shanghai
ii: song yue lou [松月楼], shanghai
iii: vegetarian lifestyle, shanghai
iv: new age veggie at the super brand mall [新素代餐厅- 正大店], shanghai
v: the yangtze langham hotel, shanghai
vi: annamaya, shanghai
vii: three virtues vegetarian, hong kong
viii: long man lou - chi lin vegetarian [龍門樓 - 志蓮素齋], hong kong
ix: gaia veggie shop, hong kong
I only wish I had eaten more noodles!