Can I cool 540 sq. ft. with a single A/C unit?
Someone would need a lot of detailed information about your apartment to determine the actual cooling load. Even assuming you have a properly sized air con unit, it seems silly to me to spend good money on an air con system and then need to rely on box fans to get it to work right. You basically should have a fan/coil unit in each room that you require to be kept at a comfortable temperature.

If you do not, one room will inevitably be too cold and the other too hot. But on the average I suppose you could claim your apartment is comfortable ;)