I need to sense if a rope has been touched, what is a safe way to do this?
I'd recommend an opposed-beam optical sensor.  PCB-mount varieties can be purchased for around $0.25 in low volumes.  Use an extension spring in series with one end of the rope to provide a little compliance (to make it kid proof, keep a length of rope in parallel with the spring so that the spring can only be stretched so far until the rope takes the load).  

Use a "flag" or other object attached to the spring to block the sensor when the rope isn't being touched/pulled, and not block the sensor when the spring is stretched a little bit due to rope tension.  You'll need to work out a mechanical solution so that the spring doesn't rotate, which would prevent the flag from returning to its position in the middle of the sensor when the rope isn't being touched.