I generally despise urban caches, particularly micros. I usually won't even bother hunting for them. When I do go hunting for them, I have found that the fake talking on the cell phone thing is a good way to do things without being noticed. Last week I had to try to replace a micro cache in a tight spot in the middle of a college campus. I couldn't figure out how I was going to accomplish it, but finally figured out that I could use the pretense of making a cell phone call (was able to put the cache in place while getting the phone out of my purse and then kick it into place while pacing around talking on the phone).
Most urban microcaches are not worth it for me. I don't want to create problems by either disturbing business owners or the police or by having someone see me and then destroy the cache. There are some very clever urban caches that I have found, however, so don't shut yourself off from them entirely. I found one on a road trip this summer that was hidden in a trap door in a flower bed and another that was stuck down a metal post (you had to retrieve it by pulling out a stake that had a rope attached that was tied to the cache container). If the owners put a lot of thought and creativity into them, urban caches can be very interesting. But I'm still generally not comfortable hunting for them when there are many people around.