ron,
from where i have traveled, i have found that the public transportation has varied from great to good and some smaller places, just so. but it will depend on what side of the fence you have grazed on too.
Walkable is a subjective word. Every city/place is walkable. It will depend on now much you want to do. Some place you can use the public (or private) transportation system easier than walking or to make your time over there more efficient. it will depend on what you want.
English language. why limit yourself to english? You may find that many of the places in the world speak english! If you travel into the back 40 or some small out of the way village, they may not but thats an adventure in itself. i have found that in all of the places i have been to, i got by with just some of the basics you would use at home, even in California. Words like, Hello, Goodbye, Yes, No, thank you....ect. But if this is a hinderance to you than by all means stick to english speaking places.
As mentioned London is English speaking and has awesome public transportation. But you will find that there are many people that dont speak english too. Like the USA, the rest of the world is becoming globalized and that includes its people.
good luck and happy trails.