I lived there for six years. Actually I just moved back to Canada in August. During that time I mainly lived in Saitama (just outside of Tokyo). I worked at various English conversation schools in Tokyo and Saitama and in my last 4 years I work as teacher in Elementary and Junior High schools in Saitama. I didnt make a lot of money there but enough to get by and enjoy myself.
I never really had any problems with the language barrier because I found most of the daily things I did English was involved. The only time it was a pain was when I had to get an apartment for myself. For that I needed my Japanese friends to help me.
I really recommend going there. Its an amazing place to visit. I will probably will go back after I finish my masters