Is there a way to change between these modes in the windows implementation?
Yes: glfwCloseWindow() + glfwOpenWindow(), which works on all platforms.
Remember: this destroys the OpenGL rendering context (i.e. you need to upload textures again etc), as well as the GLFW window context (you need to register callback functions again etc).
Also see section 2.2 in the GLFW FAQ on the homepage.
I guess this will do for me.