When I go into the store, they ALWAYS love to try and chat me up. I finally found the best way to avoid all talking with the sales people without being rude.
Be on your cell phone Call your girlfriend, best friend whatever and now it will be rude of "them" to try and have a conversation with ya.

"Yeah can I get 2 bottles of GH bloom? Thanks. :cocks head a bit: What babe? Oh yeah, that stacy girl is fricken annoying.... blah blah blah.