Visit in California with large fith-wheel -- License????

For the basic licensing requirements, as mentioned you only have to comply with the requirements from your state. I've been at the Glamis Dunes when the state of California had checkpoints in place and for us out of state folks, they just waved us through even though I was definitely heavy enough to need the special licensing if a California resident. Things like length, and double towing requirements are things you still have to comply with.