I love goin barefoot and shirtless to all the fast food places, especially McDonalds and Taco Bell. Most of the time they don't care, and many times I'll see other barefooters or shirtless guys, too! Sometimes they'll have the signs saying "no barefeet" or "shirts required" but most of the time they don't enforce it!
At a few McDonalds I have gotten into conversations about my barefoot and shirtless state. One employee told me he wished he could be shirtless, too. At a Taco Bell, this one employee complimented me on my back tattoo. If you wanna be barefoot and/or shirtless, I think fast food places are a great way to get more comfortable, and you just might meet others into it, too.