The stream cannot start until it hits a key frame. So that is most likely the cause of the long delay. It is waiting for a key frame. See if there is a way in VLC in increase the key frame interval.
Second, the rtp-live system is a pull based on demand method. So the stream is not started util the first client connects. It then remains running until the last client disconnects then it waits 10 seconds for additional connections and shuts down if no connections are made. So this long delay start will only occur for the first viewer of the stream.
We do have a module to allow you to control when the stream starts/stops. Take a look at this package:
http://community.wowza.com/t/-/54
Charlie