I am not a chameleon expert by any means so I can't answer your question specifically
However, I can recommend hiring a professional pet sitting service to care for your animals while you are away if needed. I have had great success with these types of services in the past. They are usually insured/bonded, and will come by to be trained on how to properly care for your specific pets in your home before you leave. I have had them take care of all kinds of animals - even administer meds if needed. All that and they'll bring the mail in too

Check your yellow pages or look online. It's a pretty common service.
As for how often they will need to come to care for your chameleon...hopefully someone who knows will answer that here for you. I am curious as well (I'm hoping to get a chameleon myself and am trying to learn all I can!)