For peace of mind, I wouldn't recommend barbwire. It's barely a deterrent. Mostly it's used for livestock.
What you need is a no-climb steel fence. It'll cost you a pretty penny but it will rarely fail you. Aside from a direct hit from a moving vehicle, they are rigid and mostly impenetrable to the casual bum, poacher, or wanna-be-criminal. You can get ornamental pointy-things for the top of the fence and avoid the liability of razorwire.
