That depends on your phisical conditions, if you can not walk without a wheelchair, you can visit the Great Wall with the cable car, and you still need help to get in and get off since the wheelchair is not allowed in the cable car due to the limited space. One more thing, you can not visit the Great Wall too far, you may only visit the some place where is near the cable car.

Hongkong is a metropolis and has self-contained facilities for the disabled persons. But you are still suggested to travel with your family or friends.