Using the leg as a donor source can be performed, but the yield is much lower since the hair is spaced apart further, and typically only single hair grafts are present, amongst other factors.
It is best to contact your doctor about post operative care and instructions since each doctor has a different regimen. In general, you do not need to use minoxidil after surgery.
I would not recommend stopping minoxidil for a long period of time following hair transplants as most experienced surgeons have seen patients who had significant hair loss by doing this. A week or two should be fine, but you should follow your surgeons specific recommendations.