Do portable swamp coolers work?

You bet they do. Especially with the lower humidity. You might find you enjoy it more with the air movement. I prefer them for that reason. The down draft ones offer the most air movement because of the 4 sides. Side draft that you can hang on the side of a house only have 3 sides of air and water. Be sure to maintain them well every year and you will get years of enjoyment out of it.