Yes, turn your air conditioner off if you're away (if it's not solar-powered)

Here's an interesting study done in hot, dry AZ and hot, humid GA on the energy consumption of air conditioners based on 3 usage patterns:  1) Leave running as normal when you're away for 8 hours (typical work-from-work day) 2) Turn it off for 4 hours, but schedule it to come on after that as normal 3) Turn it totally off when you're away, and turn it back on after 8 hours.  There are big savings to be had for leaving it off for 8 hours for an older AC unit and/or if you have poor insulation.