You can change languages on a Mac and switch easily between them:
- Go to System Preferences - you can click on the Apple logo in the upper-left corner of the screen and select System Preferences
- Select Language and Text
- Go to Input Sources
- Make sure the Show input menu in menu bar is checked at the bottom of this screen
A flag icon will appear on your tool box. You can use the arrow key to toggle between each language as you need it.
On a Mac you can also use the Keyboard Viewer which lets you see the country's keyboard layout you are typing in. Many countries use a different keyboard format so keys will vary for each language (especially punctuation). In Keyboard Viewer the window floats on top of your applications so it's easily viewable.