I would like to make the initial AJAX call before all the controllers get called

In Angular method run is fired before any controller is called

var app = angular.module('myApp',[]);



app.run(function($rootScope){

  // ajax call and other stuff

}

In run method you can do any job like login to Facebook, token validation and so on

Reference

Configuration blocks (aka app.config) - get executed during the provider registrations and configuration phase. Only providers and constants can be injected into configuration blocks. This is to prevent accidental instantiation of services before they have been fully configured.

Run blocks (aka app.run) - get executed after the injector is created and are used to kickstart the application. Only instances and constants can be injected into run blocks. This is to prevent further system configuration during application run time.

docs.angularjs.org/guide/module