Despite what you hear on the news etc, Jerusalem is no more dangerous for tourists than any other big city; obviously there are pickpockets etc and it would be foolish to wander alone through dodgy areas at night-time, but that does not mean that it is a dangerous place! If you are sensible and stay in the main areas, you will not be in any danger.

It's true that there are often police checks, so it may be a good idea to carry your ID with you all the time, but other than that I don't think you would have any more to worry about than in any other major city in the world.

Hope that was helpful; I'm sure you'll have a fantastic time..am very jealous!