Let me start by saying I love the flat bread sandwich's at Tropical Smoothie Cafe, but this location has some serious management/owner issues.
I stopped by about noon and had to wait 10 minutes for someone to come out of the backroom to take my order. The cashier was friendly once he came out, but there is no way you should have zero staff in the front of house for this long.
The money lost by the number of people walking out, would more then cover the cost of an additional cashier.
To the franchise owner, I would look over your surveillance video to see how many walk outs you have through out the day.