Thanks lorax! Your suggestion led me to some great resources online. I'm thinking that a solar greenhouse would be the best way to grow bananas in a hot, arid climate. Using lots of heat sinks (water, walls, etc) will help maintain a more constant temperature, especially during the winter months. And obviously the greenhouse will take care of the lack of humidity in Vegas.
The DIY section of
BuildItSolar: Solar energy projects for Do It Yourselfers to save money and reduce pollution is awesome.