I can't speak for Tokyo DL, but as far as Hong Kong goes, here is what I can tell you - English is an official language of Hong Kong, alongside Cantonese, so most people there speak English, to (widely) varying degrees.
All CM at HKDL that have any interaction with the public are required to speak fluent English. In 2 years of visiting there regularly, I as a non-Cantonese speaker have never once had any issue communicating. Not even slightly. If you're not used to the accent I guess it could be a little hard to understand some people.
Most of the rides that have commentary are in very clear English. The only attraction that does not have a full English option is the Golden Mickeys show, where the songs are in English but the MC and banter between the characters is in Cantonese. It is still a superb show, and there are English subtitles.
The Stitch Encounter has shows in all three languages, so if you choose English, it's all in perfect English. The Jungle River Cruise has the option of all three languages, however the English guides leave a lot to be desired, as they have a big job memorising a long commentary with a lot of language-based jokes and they often speak too fast for the sound system to put it across clearly. Mostly it is hard to understand and I think that's pretty bad and have often thought of commenting on it to customer service.
Festival of the Lion King is all in English, and most of the main performers are American.
Any announcements, such as before the parade or fireworks are done in all three languages.
Buying food, souvenirs etc is all completely smooth in English.
As a tourist in the rest of Hong Kong, you will find that there is also very little problem getting around with English in the main tourist areas. Once again, companies tend to have as a requirement for people working with tourists that they speak fluent English. In the more local Chinese districts, it's a bit more interesting but you just get good at sign language. Staff in hotels etc speak fluent English.
Hope that helps.
