This time of year the swamp cooler works great. The outside temps are around 90, but the humidity is in the single digits. That makes for very effective cooling and the air being circulated is probably in the 70's. Things won't be so good in July when the monsoons start kicking in. The higher humidities means that the air doesn't get cooled as much. On the other paw, the thunderstorms that are generated do quite a nice job in cooling down the outside air in general.
There is a big push around here to get people off of swamp coolers and on to air conditioners. I think it must be a conspiracy by the power company. I remember the $300 electric bills in July and August when I lived in Yuma. While the house was always nice and cool, it came at a price. Here the push is in the name of water conservation. I guess someone should do a study on how much water a typical swamp cooler uses and how much extra water would be needed at power plants to generate the extra energy needed to run an air conditioner. I'll stick with my trusty swamp cooler and the $50 electric bills, thank you very much.
EDIT: Wow! Today is my 3 year LJ anniversary! I can't believe I have kept up with this thing for that long! Thanks to all who have helped make it a fun trip so far!