Instead of using Maya cloth try it this way, works for me and less rendering time. Create a nurbs plane for your flag, turn it into a soft body object and add a turbulence field. Adjust the goal weight attribute to give wind 'strength' effect. Lastly you need to give the flag a direction to 'blow'. So you need to create an expression (coz it's easier) go to the phase X attribute of the turbulence field, right click on it and enter -

turbulenceField1.phaseX=2*time;

Of course this only works for a windy flag...