To best insure that people 'keep off' your performance (stage) area then you'll need to be actually set up 'on' a stage. If the venue doesn't include a stage, then a portable 'platform riser:
http://www.wbsshelving.com/furniture/stagesportable1.htm
http://www.i-weiss.com/products/stage/portablestaging/


might be in order, and can be purchased or rented (by the day) from local equipment rental stores. For my solo one man arranger vocal/keyboard act, I find a 4'X6' riser (with skirt) minimally sufficient if positioned against a wall (to prevent me from falling off the back.

Scott