If you want to monitor the ARES nets for northern Colorado. Don't call in unnecessarily, these are not general info nets like normal. But if you need help immediately or can offer help to something you hear specifically, you could make a request by asking to be recognized by the net controller. All the stations you hear have trained and practiced together, it's not really an ad-hoc net.
Larimer & Weld Counties
W0UPS (NCARC) - 447.275/PL100Hz/-5MHz
W0IA (RMVHFS) - 146.760/PL100Hz/-0.6MHz