Always check temperature forecast in the bottom of canyon. Be prudenct if temperature is over 90 and no hiking experience in such climatic environment.
Majority of people can do it if the weather is mild. The easy trail is from south rim down to Colorado River and back to south rim. Distance is 10miles and elevation is 4000ft.
A few hiking partners (including a beijing lady, the founder of hiking group in bay area dragon, www.bayareadragon.com) did round trip of grand canyon: from south rim to north rim and back to south rim. It is notoriously called "Death March": distance is 45miles and it tooks 22-23 hours to finish.
