Some people can speak basic/broken English, but it'd help so much if you could learn at least some basic Japanese to not only be useful if you need help, but to impress the locals too. :p

Thanks for answering. I am currently studying some Japanese and hope that it helps:)

Never count on the English of strangers to get around in Japan.

Learn a little, and if you are not afraid to get embarrassed and communicate in hand signals and and broken English mixed with little bits of Japanese, from my experience you will be fine.

But only in the big cities, and the touristy parts at that.

Leave them and don't expect to speak English all day.

Saying that I travelled all over with really terrible spoken Japanese, I barely even knew direction vocabulary, and the Kanji for 地下鉄chikatetsu-subway
scared the life out of me in how complex it was! I survived and had a great time.
I found it really useful in reading signs and using machines that I could read hiragana/katakana and figure out some basic words though.
I got lost a couple of times and could vaguely spit out, where is the train station, then not understand a word in reply and I was lucky the people who helped me had broken English and didn't mind drawing me little maps/hand directions etc. Also funny issues in shops where I didn't know what a ふくろ - plastic bag, was and why they kept asking me if I had one/wanted one! So conversations went round in circles, but it all worked out somehow.

I digress into rambling as usual...

tl;dr

If you stay in the very touristy areas like Central Tokyo/Central Osaka and learn a few travel related basics, and are the sort of person who can find humour in embarrassing situations, and be resourceful with non-verbal communication you will be fine.

The more you learn the easier time you will have, but as MMM said don't rely on them speaking English, try plan everything out so you don't need help too often.