Westchester is slim pickins in the culinary department. Buggy Whip is good but gets pricey. I don't know if you consider these "fast food", but there is a Boston Market and a Panera on Sepulveda (Boston Market is at SW corner of 89th/Sepulveda in front of Ralph's, Panera is between Manchester and LaTijera...in the strip mall with Trader Joe's and Mervyn's.)

For breakfast everyone likes The Coffee Company at La Tijera & Sepulveda Eastway. Grinder's is also good...sort of a local small-chain version of Coco's or Baker's Square...NW corner Manchester at Sepulveda (enter off of Manchester, it's hidden away behind the 76 station.)

I haven't gotten to the rib joint at 84th & Lincoln, I hear it is nothing extraordinary but decent for something different.