If you are going to go with a tour - excellent tours are provided by Green Olive tours (joint Jewish-Arab company) Just double check with them a couple days before if the tour is operating. The tours are an amazing insight at life on the other side of the wall, and you get much more than the typical coach tour tourist site experience. Their tour of Hebron was an amazing eye-opener.

Otherwise, bus 21 departs from just outside Damascus Gate, if you are a foreigner and white, you are not gonna get hassled at the checkpoints. As for security, I dont know exactly what you are worried about???