DIY carwashes can indeed be dangerous places. A friend of mine's brother was shot and killed at one a few years back; had gone to wash his brand new truck, some other creatures decided they wanted it. They were caught and prosecuted and are in prison but he is dead.
A couple of years ago I was using a carwash in a good part of town in the middle of the day with other people around, and a couple of guys pull up at the front of my bay and roll down the window and ask me if I wanted to buy some perfume. Yeah, right. I (this was before my entry into gun life) stopped right by my driver side door with the wand in my hand and told them to go away. They asked again and I said a little louder, go away and leave me alone. They did, but I was ready to fill that car with soapy water and jump into my car and back out.
Agree with springmom now, it's best to wash at home, or in one of those with a waiting room.