No there is no public beta out yet but if you live close enough to Redmond, WA Microsoft would like you to come on in and try out the latest internal version. Get a chance to test your demos early.

If you have a code base you would like me to take along and test please let me know and I will see how much time I have. Since its under NDA I will not be able to give you feedback but I can make sure MS see any issues or bugs which might mean the beta is in better shape when it comes out.

Check out Mitch's announcement of the XNA GS 2.0 testing labs