Deaf people may not be comfortable using their national spoken or written language; foreign languages may present even more problems.
Deaf people who went to special schools for the deaf may have had little or no instruction in foreign languages. Learning a foreign language after age 20 (and some say: after age 12) is very difficult for anyone. If your first language is a sign language, learning to read and write a foreign language is even more difficult.
Lipreading a foreign language is almost impossible.
Do not assume that deaf students can read English or other foreign languages.
On the other hand: most deaf sign language users are very good at learning foreign sign languages, and at communicating with sign language users from other countries.