It would be hard for me to shop somewhere I normally go to. I don't eat fast food or even casual restaurant food unless I'm shopping. I don't need to go to those places.
I do shop at Kroger even when I'm not mystery shopping, but I don't do things drastically differently than I do in a mystery shop. I buy approximately the same things, and spend about the same amount of money.
But I don't really eat at many fast food places unless I'm likely to get my money refunded. I like fried chicken, so I will occaisonally go to Popeyes or Slim Chickens. I know there are Slim Chickens shops, but I got Nikki'd and the MSC won't even let me apply for the shops, even though I'm not deactivated. Otherwise, if I'm out and need to eat I'll get myself a sandwich at Publix.