"The keyboard layout change is by design, and I don't know of a solution, except for using instead of RDC another remote desktop solution such as VNC.
You might try to see if this behavior is not improved in the latest Remote Desktop Connection 7.0 client, but I wouldn't hope for too much.
The only help I can offer is the information that in Windows Vista it's possible to configure international settings from the command line. Writing such a script might simplify getting rid of the unwanted keyboard. If this interests you, see this article."