The important thing to remember is Disney isn't like Chili's in the mall, they won't just take a name and seat you when they can. If they are booked up, they can't take more guests. Every once in a while they'll be able to work in a walk up party but that is the exception, rather than the rule. So if they get online and see that no ADR is open for a group of 7:00 at the time they plan to go, then there is no opening for a group of 7 at the time they plan to go and they won't be seated.
Now, it never hurts to ask but it does waste time that could be spent doing something else. I suggest trying the Wave downstairs or even Contempo Cafe next to CM. Both have WAY better food. That should tell you just how poor it is, when a QS is better