EB what kind of fast food?
I think the fastest growing / most popular new franchise out here is Chipotle... I'm so addicted to that stuff sometimes. Probably eat at Chip' 3-5 times a week.
www.chipotle.com
Maybe you can get some ideas there if you aren't 100% sure of what type of food you want to serve. Mexican food (especially the way they do it) can be quick and easy... and is very popular on the west coast right now. Not sure about out there.