I'll second what Treadwell said - PVC and plexiglass don't really melt all that easy. It does depend on what bits you use, though, and how long you keep it in that one spot.
You will really want some bit that gets the plastic up and out of the way. You'll be throwing a lot of plastic bits around, and they are a bit hot, but nothing to worry about if you are properly dressed and have the normal safety gear on.