When I leave town, I usually have a family member come and stay. All of my cages are automatically regulated with lighting timers and misting systems, so all there really is to do while we're gone is toss crickets/superworms in. I label each cage with the chameleon's name and how many crickets/worms they should be given. I leave my vet's number handy just in case anything happens and I always notify my vet when I'm leaving so that he will know what's up if he receives a call. There have been a few times when I had to leave town and I had a chameleon who was receiving daily medical treatment or who was ill. If that's the case, I usually transport the chameleon to my vet's office and make arrangements for the chameleon to stay there. It's not cheap, but at least I know the chameleon will be cared for properly, as it's too much of a burden and risk to ask a relative to administer medicine or treatment.
My relatives seem to really enjoy staying at our house when we're out of town. They always have lots of stories about their interactions with the chameleons when we get back (nothing I haven't seen a hundred times, but to them, being able to observe a chameleon daily is new and everyone seems to enjoy it).