A/c's tend to dehumidify a bit, not a whole lot, but some. you should be just fine. the main issue with an a/c is finding the balance between your ventilation and cooling. you have to get fresh air in to the grow space and take old air out. too much air exchange and the a/c wont be able to keep up, too little and your plants will suffer. in a small space like yours, a simple co2 system will help a lot. a couple homemade co2 bottles should be all you need, but you could get a tank and control valve. depending on where you live and how hot your area gets during summer, you may be able to control your heat with enclosed, ducted hoods and a strong inline fan.