Old thread, but hey, it's valid!
I've done last minute prints at Walmart (WHCC for everything else), and I get great colors I get from their Fuji Frontier printer. I'm sorry to say that no one in my immediate area (within 25 miles) has anything other than the cheap Kodak laser-type kiosk printers so I don't bother going with that glossy mess.
Understand that photo-managers and employees can get raked over the coals if a photo printing job results in a copyright complaint/suit. I'm not defending the attitude part of the whole deal, but perhaps their overzealousness is understandable.
It's either that or how many ethically questionable shots they get to process in one day.
I for one made sure that before I started printing there I told them who I was and what I did. They gave me a form that states who I was and that I'm the copyright holder and kept it on file. It's been a couple of years and I don't get asked anything as long as they look at my file. If they give me attitude, I tell em to look at my file as they should have and soon I'm on my way.
It's all about the manager and how he/she runs their outfit!