McCarran is a rather large airport with quite a number of places to eat. I have found that waiting for a cab can be compared to waiting in line at Disneyland. You are marched down from one end of the area to the other and when it's 100+ outdoors, that can be alot. I will often take the shared shuttle as I can usually pay, jump right on the shuttle that has A/C running and just relax.
Safe travels!!