Yes running just the signal wire is acceptable, the ESC ground plane is common to all circuits though the lipo power leads so it doesn't need the ground connection to the controller. The controller is on the same ground plane as long as you are using the same battery to power the ESCs along with the rest of the electronics. I usually just pull the red wire and leave the ground in place because its already there, it will work exactly the same with just the signal wire.
Ken