I've tried it at two Walmarts. Unfortunately, you have to deal with the "greeter" ... ... the first greeter could barely speak English, and said "No" without listening. The second greeter was much more accommodating, and was happy to let me bring it into the customer service area. And the customer service folks were even more accommodating, offering to watch my bike while I went to grab an item.

Overall, though, I agree that if given the opportunity to "think about it", most Walmart employees would say NO.