I would also use a "split" system. They can be very efficient and you can do it yourself provided you have the electrical taken care of. The Mistsubishi and Fujitsu units are supposed to be the best according the Carrier guy that installed my second unit. He had just moved to Las Vegas from Hawaii and they use a lot of these type systems.
Here is a link to what I am talking about.
http://www.ductlessdepot.net/products-type-1.html
They also have some units that will mount into the ceiling instead of the wall.
I have used these in two applications. The first was the garage in a previous house. Part of the unit was installed on the wall inside and you had to run a condensate line outside and the line to the outside part of the unit. It was a very clean install and kept our large (20'x30') garage very cool in Las Vegas.
The other area I used it was in a smaller 15'x10' room that housed all the equipment for a 450 gallon fish tank (tank included). It was in a pretty humid environment and also very hot since I was running various pumps as well as four 400 watt light fixtures. That application was much more complicated as I also had a dehumidistat/thermastat installed that would run an exhaust fan to "help" the AC unit.