Just get some "barrier" fencing, it's plastic, cheap and easy to move, Just stake it in the ground. Here's a picture of it:
http://www.acehardware.com/product/index.jsp?productId=1275483&cp=2568443.2568444.2598671.2602631.1260341
(I dont' own Ace, nor do I work for the company, so no conflict...