Having worked in a mall environment (before social networking was popular) I witnessed several book signings. The attendance was usually dependent on several things: author popularity, advertising by the store or author, genre, etc. Now-a-days I suspect some good networking would improve the odds. Most of the authors were local and first time novelists. Some shoppers might be drawn in out of curiosity, but most were too busy looking for pajamas for aunt Jane.
The exceptions were pop-artists and sports celebs. When Buffalo Bills QB Jim Kelly came out with a book about his son's illness, thousands of fans flooded the mall (not so much for the book, per se, but to see the once great legend).
I would tend to bet that a better route might be via author website and networking. I probably have purchased more Kindle books from leads found in this forum (or related blogs) than any other source.
Just my two-cents, Jon.