WW won't help/work unless you really make a commitment to it. And yes, with WW you can absolutely have fries at a fast food place- but if you're actually *following* the program you'll only do it every once in a while, not daily.
Basically WW is like a budget for food. You have your points that your allotted, plus your musts (veggies, fruit, dairy) and then you figure out what else you want to eat with the rest of your points.
Of course, that's the old program and I understand that there is a new program... I'm not sure how that one works.
HTH!