I don't own one, nor will I ever get into food sales.
I do know it's location location location, just like everything else though.
We have a family friend who opened a Del Taco on a main blvd. in the valley, like Burbank area. She did amazing and soon had profits to open more. She tried another Del Taco in Northridge that tanked in 4 months. She even tried a McD's in Sun Valley and it tanked as well.
My mom used to be the marketing director for Shakey's pizza here in SoCal. There were mediocre chain doing minimal business, mostly repeat customers and private parties. She marketed to all the local schools, brought ovens for lunchtime to the junior and high schools, and sponsored fund raisers like mad and business boomed. She also worked a deal with In-N-Out in a joint venture with team sponsorship. I think getting into the community is a huge sale point.