The usual recovery mode/installer task bar has several menus. Terminal is usually reached from the Utilities menu.
Upon boot, the task bar that is first presented is that shown with the "language chooser" dialogue, which just has a language chooser menu.
Once the language has been chosen, the task bar should change to the usual menu, but instead the "language chooser" task bar remains.
In order to get the correct task bar to appear, moving the cursor around at the top of the screen (making the task bar appear and hide repeatedly) will quite quickly (only took me a few seconds) result in the correct task bar appearing.
You should now be able to open Terminal from the Utilities menu.