I just talked about this with my contact at WDFW. Call the Hotline number as soon as you see the violation, and the dispatcher will send the message to all officers currently on duty. Getting the license plate number is golden. Be discreet as possible, I was seen photographing bait fishermen at Munn Lake recently, and the guys took off immediately. Of course they came back at he same time the next day, and were busted, but they usually are bright enough to realize they've been identified. License plate numbers with vehicle description, number, age and gender of poachers seems to the most important details they ask for.
I have plenty of conservation signs available, and will mail them to you. Even if the sign doesn't prevent determined poachers, posting one on site prevents claiming ignorance of the regs.
Keep up the good work.