Installing Coax & Cat6 in 2-Gang with Electrical?
Yes you can, as long as you keep the conductors separated. However, you should likely avoid it if possible. Common practice is to keep power and communications circuits in separate stud bays.

National Electrical Code allows you to put power and communication circuits in the same box, as long as all the conductors are separated by a permanent barrier or listed device.


  National Electrical Code 2014
  
  Chapter 8 Communications Systems
  
  Article 800 Communications Circuits
  
  800.133 Installation of Communications Wires, Cables,
  and Equipment.  
  
  (A) Separation from Other Conductors.  
  
  (1) In Raceways, Cable Trays, Boxes, Cables, Enclosures and Cable Routing Assemblies.
  
  (d) Electric Light, Power, Class 1, Non–Power-Limited
  Fire Alarm, and Medium-Power Network-Powered Broadband
  Communications Circuits in Raceways, Compartments,
  and Boxes. Communications conductors shall not be placed in
  any raceway, compartment, outlet box, junction box, or similar
  fitting with conductors of electric light, power, Class 1, non–
  power-limited fire alarm, or medium-power network-powered
  broadband communications circuits.
  
  Exception No. 1: Where all of the conductors of electric
  light, power, Class 1, non–power-limited fire alarm, and
  medium-power network-powered broadband communications
  circuits are separated from all of the conductors of communications
  circuits by a permanent barrier or listed divider.


Here's an example of a listed device:

From a Carlon sales brochure