I'm glad he seems so social. First, how old is he? If he's still a very young cham his hormones have not bloomed yet, and that is temporary. Once he matures he may not be so tolerant and he will most likely get a little more territorial. Not a bad thing, just a normal cham thing.
Still, for his own sake I feel I should caution you not to misinterpret his behavior. We are very social beings and it can be hard not to lay our own social desires onto an animal that isn't wired the same way emotionally. I always remind myself...do I KNOW he's happy? Why or why not? What does his behavior really mean? What does his color change tell me? How does he show that he "loves" car rides? It's a pretty unnatural thing for a cham to watch the world whizzing by and he may actually be mesmerized and fearful.
For example: taking a nap while he's sitting on you is not a sign of happiness, its a sign of anxiety, extreme fear, or illness. If he sits motionless he isn't necessarily contented, he's trying to disappear because he feels threatened. If his coloration gets bright when he's being handled it doesn't necessarily mean he's glad to be handled, just that he is aroused. When he wants to come out of his cage it could be that he's indeed happy to roam around on someone, but it can also mean that he feels too confined in a too-small cage and will do anything to escape it. People often say their chams love to climb onto someone's head...it is an attempt to get as high off the ground as possible as that means safety.
I don't mean to burst your bubble about your little guy, just add a caution so you don't miss a sign of trouble before it causes problems OK?