As this was our first year. We were wondering about the gameplay. Can a coach and the drivers use radio communication to talk during the match.
No. Wireless signals are prohibited during the gameplay.
Thank You.
Radio communication is also a bit unnecessary. The coach can stand right behind the drivers.
<T26>Devices used solely for the purpose of planning or tracking strategy of game play are allowed inside the ALLIANCE STATION, if they meet ALL of the following conditions:
Do not include any form of enabled wireless electronic communication (e.g. radios, walkie-talkies, cell phones, Bluetooth communications, WiFi, etc.)
Would this mean that wired communications are legal? 
Yes, I believe it would. I better brush up on my Morse code::rtm::
<T25> The only equipment that may be brought in to the ALLIANCE STATION is the OPERATOR CONSOLE and non-powered ANALYST-to-FEEDER signaling devices. Reasonable decorative items, and special clothing and/or equipment required due to a disability may be brought into the ALLIANCE or FEEDER STATIONS. Other items, particularly those intended to provide a competitive advantage for the TEAM, are prohibited.
You really don’t have any need for a radio.
You can pretty much stand with your mouth 3" away from your driver’s ear if you wanted to.