Did you try looking in a dictionary?
Student or Learner
What is the meaning of “are welcome” in the following sentence:
Disabled visitors are welcome; there is good wheelchair access to most facilities.
It means that, because most facilities have good wheelchair access, disabled visitors don't have to refrain from visiting.
PS: I guess the phrase "are welcome" is a fixed structure in touristic brochures. Of course, all visitors "are welcome", that's why resorts/museums/restaurants/fun parks etc. are opened . If they did not welcome visitors, theyu would have to close shortly after opening.
Please be aware that I'm neither a native English speaker nor a teacher.