Personally, I would feel safer to just leave it in the car. I have to do that often anyway. Just keep it out of sight, as well as anything else of value, so no one sees a reason to break in the car, to start with.
Your gun is safer in the car then at the motel safe, probably. When I go to church, I can't legally wear my gun, but I want my gun when I go back home. There's really not much choice, but to leave it locked in the car out of sight. Other situations are similar.
It's the law of averages, and odds. Do I want to leave it in a safe at a motel, where someone already knows I have probably left something of value, or leave in a car among hundreds of others, on the whim that thieves with pick my car. Of course I don't drive a new or fancy car, either.