There are a few other common restaurant chains in there.
http://www.witnessesuntome.com/2011/04/dining-with-the-cia/
It is a pain in the ass to get in your car and leave for lunch.
Starbucks is there too
http://rdanderson.com/dossier/entries/cia.htm - no surprise.. they're everywhere.
I don't think that the workers get a clearance. They have no need to know and the public areas forbid classified conversations. They probably get a background check.