People in Japan are incredibly nice. I would not worry about the language barrier much... now you're not going to find everything in English, and not all are fluent in English, but there are lots of pictures, the transportation system is easy to navigate, and you can get by with lots of pointing haha. Again, most people are willing to go out of their way to help.
Cheap times of year will probably be winter and summer. Fall in Japan is beautiful, as is spring (cherry blossom season). Winter in Tokyo is OK, it's cold and bleak, but I had no issues (besides being cold). Summer is awful (humid, wet, etc.) so I would not recommend.
Japan is by far the coolest place I have been to. Fascinating place. Also, every single food dish I had was amazing (like, the Italian food was mind-blowing). You'll love it!