Welcome aboard Megan
You can learn a lot here. I hope you take advantage of the possibilities. Another site, similar to this one, is Just Plain Folks: http://www.jpfolks.com/
I would urge you to rethink the "Demo My Song" strategy and put your efforts into finding music writers to work with. It'll cost less (as in nothing except time) and you'll learn more. "Demo My Song" is just going to take what you've got and jam it into a formula with as little effort as they can manage. A co-writer is going to come back to you and say, "Uh, Megan, this isn't going to work because of this, or that." And then you'll have to work to make the song better. That's a good thing.
Another site to check out in your search for music writers is http://www.kompoz.com/