There are also Gitorious and Bitbucket (supports Git and Mercurial) and others.
You can also host code yourself: I just set up Fossil for a small project and its very easy to do.
Try them, and see what suits you.
ergophone is entirely right that marketing is going to be the difficult bit. Lots of people and organisations have been disappointed because they thought all they had to do was shove code on Sourceforge and lots of people would rush to get involved.
That said, you are unlikely to lose much by opening it, and if people actually use it, at least you will get some bug reports and ideas. If you are lucky you do manage to get other developers involved.