I take dogs to work all the time but I have a lot going for me. I work for a small, private college so I park in a small, private, security patrolled lot that is heavily shaded by trees and is right outside my building. If I'm late and don't think I can get a spot in "my" lot, I don't bring dogs. The other faculty and staff who use this lot regularly are very familiar with the "dog van" and my dogs, so they are ignored and no one is surprised to see them going in and out. Since I walk them around campus or do training on breaks all the campus security offers know them and are aware of the "dog van" (and most of them love it and keep teasing me about training my dogs to detect drugs for then).
Any dogs in the van are kept in crates with comfy bedding and a water pail. That is mostly so that if people look in they don't think my dogs are "in jail" or dehydrated. I have small locks that lock the crates since usually the windows are open (even in the dead of winter they are cracked).
My dogs are very accustomed to being in the van and are quiet. They wouldn't bark unless someone actually opened the van and tried to do something. People walking by or even peeking in get no reaction.
I'm really careful about the weather and temps. I might bring one if its 60-70 but only on a cloudy day that is not humid. Windows are always down, even in the winter. Also like I said when the leaves are on the trees, my lot is entirely shaded and I also drape shades inside the van which usually are not necessary but give passersby the right impression. Normally I bring dogs in the fall and winter. When I get a new puppy I get a fall puppy so I can have it in the van at work and let it out several times a day.
I'm lucky to be able to do this because of where I work and the level of privacy and security. Honestly I feel my dogs are more secure at work in the van than being locked in my house. Anyone could pretty easily break into my house...