As people have said, having a no right-click script will not deter the folks who really want the picture - there are so many ways around it.

But a bigger reason to really consider not using it is that a lot of people use the right-click legitimately (for example, to go "back" on a webpage) that you might end up making people mad by using it. I prefer to add text (like a © mark and your business name) to the photo instead of disabling right-clicks.