In settings, language & input, tap the icon to the right of Android Keyboard, input languages, deselect use system language, then you can select multiple languages. When you type a tiny keyboard appears in the notification bar, pull down to select the language of choice
No problem. The other two posters also listed alternate ways to get to the keyboard settings. Those come in handy if you ever download another keyboard and want to switch between them.
Sent from my totally awesome Sprint Galaxy Nexus, even if I don't know all its secrets yet.