I know of American stations like CONELRAD, but I can't find any information about Spanish (specifically in Mexico) broadcasts.
You might be confusing some things. CONELRAD was a forerunner of what we now call the Emergency Broadcast System, which would give instructions to the US population in case of emergency, such as nuclear attack.
News and what some might call propaganda broadcasts were provided by the Voice of America, Radio Free Europe, Radio Liberty, and (to Cuba) Radio MartÃ.