Good post Greywolf, I almost forgot you should have signals; (examples)
Safe House is owned by Pro-Government Liberal Veteran. Each day the Pro-Gov-Lib-Vet goes out and hangs a flag from him front porch. (Anyone like my cover ID?)
Red USMC Flag: Under Survelliance, Proceed with Caution
Rainbow Flag: Safe to enter
POW/MIA Flag: STAY AWAY!!!
US or Occupier's Flag: Need Aistance
UN Flag: False Safe to Enter Flag, e.i. its a set up

Flags & Meanings should be rotated once a week or group specific.