Sorry, but I see no correlation between the restaurant someone worked in and their abilities and capabilities. A great waitress can be wasted in a poor restaurant, and a poor waitress will certainly drag down a great restaurant's reputation.
When I worked for an insurance company, I had to interview many people for underwriting jobs. We could not really look at what their previous employer did as far as profitability was concerned. Our interviewing training taught us to ask questions that were unique to our company, ask the same questions to every applicant, ask questions that would show the applicant's strengths in their eyes, ask questions that would be "tell me about a time when..." relating to a positive experience and also to negative experiences, etc. By tailoring your interviewing to questions relating to how you want your employees to act, think, behave, etc, you should get a feel for how they will fit into your organization. I certainly wouldn't hold it against an applicant if they worked at a restaurant that is perceived to have bad service...maybe that is why they left!
