Now you are disecting people into numbers
In my experience Managing Restaurants in the past, my best workers were those that got paid what they were worth and given goals within the business.
Another problem is if they come and go every 6 months, your "regulars" that you build up and I assume that is what you are basing future success on, that and word of mouth, are only relying on the food. The "cute young girls" are coming and going and they don't get to know anyone that well, assumingly you when you are out of the kitchen.
Have you considered paying one person a good and decent wage with future direction that is on the floor, playing hostest and assisting taking food out etc, etc, that the people can warm to, and the customers can aclaim friendly, great service in addition to food. Wouldn't you think that would make your turnover even greater for a small price.