Use simple English and write things down.
If you should encounter any difficulty when trying to communicate in English just use very simple slow English and if that doesn't work write it down. Most Japanese have a lot of passive English knowledge from their Jr. high school days but just have not had the chance to use it so may be a little rusty but will enjoy talking with you and it helps to build their openness to others and their self-confidence. :-)
Career Coach Brent