I'm afraid fdmaxey is wrong here, he/she has described sign language...
哑巴英语 is a Chinese expression to describe a Chinese English student who is able to read and write English but whose oral English level is very low, and is therefore unwilling to "开口"
I'm afraid English doesn't have such a phrase, you would have to use a sentence to describe such a person:
for e.g. His reading and writing skills are great, but his oral skills are terrible,
OR
He can read and write English very well, but his spoken English is not up to par.
The Chinglish for 哑巴英语 is dumb English...but please don't use this phrase. Western people won't understand, and might even get upset over it.