In terms of getting around - everyone speaks english. If you plan on taking metro/public transport - get an Octopus card. You can either do that at the metro stations or 7-11.
Street food is generally okay, as long as there are a lot of people eating there. I eat from vendors all the time with no problems and I have a very "delicate glass stomach" as my dad says. I don't eat raw food though, without taking it and washing it myself - regular travel rules apply for drinking things.
The airport is huge; don't be surprised to see military there with machine guns - that's just their security.
If you're going to the New Territories - green cabs are cheaper than red (the green ones are set rate, and the red ones are by the hour, I think).
If you have respiratory difficulties, bring extra ventolin. I almost never need my blue puffer but I was pretty reliant on it during our trip.
HAVE FUN Can't wait to see your pics!
