I'd love to go, and have used google translate extensively, but am concerned about not being able to read signs. I agree that travel should be challenging, but not to the degree that it kills the experience.
GPS is in everything. So hailing a taxi via an app is a not huge issue largely. And wherever you go you can use Baidu maps to tell you where you are vs. where you need to be.
Subways are fine for an English speaker, as long as you know where you're going and check the interchange. Rush hours may be a little crowded.
As long as you've done your research where you want to go, you should be OK. Wouldn't do it with family until getting used to doing so for a few days. eChinaCities should be avoided as their despite their Google et al search listings being very high, are mainly paid content. Find a website local for the city, e.g. is in Beijing then thebeijinger.com should be fine.
Do not follow someone with good English pretending to take you somewhere like a tea shop, restaurant or art gallery, or really anywhere. Don't say the nation you're from, just be assertive in refusal.
Have been in China for a few years in a few cities, mainly north.
I think this depends more on the traveler than on the city/nation. I don't think there is anywhere that language necessarily pigeonholes you to tourist areas - it's simply how comfortable or uncomfortable it makes you.
That being said, I think you would have very good luck in Hong Kong, for obvious reasons. Beyond english accessibility, I find Hong Kong to be the most fascinating and interesting city in the world. I love to be there and miss it when I am not.
If you can find some kind of personal connection there - a meetup or hackerspace or ... anything ... it is definitely helpful and will get you off the beaten path much more quickly.
HKGers should check out DimSumLabs ( https://www.meetup.com/dimsumlabs/ ) as a really nice bunch (at least when I was there).