I live in Phoenix, so i can tell you a thing or two about hot temperatures in the Summer. Anyway, i just got into brewing, and ran into the same problem. I combed craigslist for a few weeks, and found a nice dorm-sized mini fridge for super cheap. My ale-pail fits perfectly inside, and I've built a temperature controller from a $20 aquarium temp controller that's commonly sold on ebay.
I just set a temp on the controller, and it kicks the mini fridge on and off to keep it there. For the $60 I have invested, it's worth every penny. On the cheaper end, get a big rubbermaid tub, wrap a towel around your bucket/carboy. fill the tub up about 8" with water, and drop some frozen water bottles in there. The cold water will wick up the towel and evaporate to cool the beer.