If I walked in to a designer boutique wearing a cheap but well put together outfit, would I be accepted?

Yes you would be. Now I have walked into Neiman Marcus wearing clothes I got from Kohl's and they treated me fine. The thing is if you walk into the Boutique with class and elegance they will treat you fine. Remember because of the economic turmoil we are in many of these Boutiques are desperate for sales so they must treat people with respect. The mall closest to were I live, just closed down a Dillard's and in the Boca Mall (a VERY high end mall) Theory, Steve Madden, and other boutiques have closed down because of the economy.