Do you need an interpreter? That may make things a bit rough as you'll have to find a guide to assist, I am not sure about this.
Rude and uncustomary to eat while walking in Japan. Has to do with cultural manners, asians prefer to sit down and eat instead. Eating on public transportation is also frowned upon.
Don't smoke while walking.
Not all japanese are great at english, even though their schools incorporate it. A good amount of japanese don't put basic english composition and grammar as a part of their lifestyle, so be used to trying to use fragmented english.
If you can, learn some of the basic hiragana and katakana. It's actually not too hard and there are language charts available. Many non-kanji words can be looked up in a dictionary or online.
$ 1000 yen (¥ or 円) is equivalent to ~$11 US. You will see the signs around fairly often. ¥40,000 ¥7000 and so on.
