"I don't know English" and "I don't speak English" are both fine.
Since your elders are traveling, they can even say "No english" which is
easier to remember and people will be able to understand as well.
※ 引述《SONYko (SONY子)》之铭言：
: Hello everyone.
: There is no English course when the elders are student.
: But the elders that I know will go abroad recently.
: So I am preparing English/Chinese list about travel.
: To avoid being gotten in a word by foreigner,
: I list "我不会说英文" into document.
: But I am confusing how to translate?
: > I don't know English.
: > I have no skill to speak English.
: > I don't know how to speak English.
: > I can't speak English. (possible cause misunderstanding?)
: > I don't speak English. (possible cause misunderstanding?)
: How about your opinion?