Portables are usually a pore choice in a grow room because they are really under rated and they need to be exhausted via an tube so you can send the hot air out that is generated in the unit and they often have problems leaking. I have read numerous threads on other boards and if not all thought that the portable was a bad choice. If your in a low humidity area then a Swamp/Evaporative cooler will work and if you can vent a window AC unit then it will be the best bet, but perhaps you will find a person who can naysay my info. Also, the portables will suck out the CO2 from your room the majority of the time.
Adieu