I configured a US (English) keyboard in Ubuntu 12.04, so I’ll share the method.

1. Click the gear icon in the upper right 2. "System Settings" → "Keyboard Layout" 3. Click the + (button), select "English (US)" in "Select Layout" and "Add"

You can switch between English/Japanese using the [Ctrl] + [Space] command.

Reference Information

• 英語キーボード　設定　Ubuntu編: マッキンダムの空から

That’s all from the Gemba.