sleep in car (for the true budget traveler)

I have decided to kill two birds with one stone for my 24 hour lay over in Guam. Going to rent a car upon arrival and sleep in it, then use it to tour the next day. I know there are some like-minded travelers out there shaking their heads, "yes, yes" right now. You are not alone!

My questions is does anyone know a good place to park the car and sleep in it. Somewhere one would not be bothered?

I did this about 12 years ago and parked the car in the car par of a luxury hotel, can't remember which one. It was no problem to use the hotel facilites like bathrooms and I snuck into the pool. Don't know if that would still be true today though.