a little additional to JoeScanner's post...
If an event is ONLY in Central Prcnt, like most protests or political rallies, most likely it will be on Cent Tac 1. But if it is a larger event, as he noted, check one of the metro channels.
Regarding Washington county, Common Law 1 & 2, and Public Safety 1 & 2:
PS1 (Public Safety 1) I have noticed being used for traffic details. Common Law is usually for officers from different agencies to meet to discuss stuff.
I have, in the past, heard PS2 used for training
just my 0.2 cents
PS. Speaking of parades, I am going to be helping out at the Hillsboro 4th of July parade, there will be ham radio operators helping out with emergency communication, I will let you all know what freq we will be on.
Will