Is there a fee to use the shower truck? I also have a camping shower, but will save the packing space and water if the truck is free or cheap (and a hot shower in the AM beats waiting around all day for my water to warm up in the sun....not that I'd be waiting around at camp for that either!)
I bring mine empty and fill it when I get there. I don't take showers with it, I use it for washing my hands and rinsing dishes. It heats up in less than an hour in the morning sun, as long as it doesn't freeze the night before.
It's only 2.5 gallons.