For a do it your selfer, the swamp cooler seems to be the best bet for me. how hard is it to keep the cooler clean? Depending on your location and the location of the cooler it may be no trouble keeping it clean. buy good filter media and it lasts. Every year at the end of the season I drain and clean the cooler very well. Then I put an oil cloth type canvas cover on it with 6 ratchet straps. 7 years later, my cooler still looked new. Coolers are cheap, easy to install, easy to maintain and cheap to replace. Ac is none of those things. Obviously if you have some sort of respiratory problems you may be better off with the AC. I have lived in probably a dozen different houses with Evaporative coolers and a few ith AC. I would much rather have the swamp cooler.

Irving just remember to open enough windows. I think the instructions I have seen say open the furthest windows and put a dollar bill on the screen. If it sticks open the window/windows further. Just to the point it slips down. All that air needs to go somewhere.