How to activate RTL in wordpress twenty eleven

Do normal englsih installation

Download a copy of arabic wordpress.

Copy the file wp-content/languages/ar.php from arabic version to english version

Go to wp-config.php and add define(‘WPLANG’, ‘ar’);

Khalas, you get an Englsih wordpress in RTL

Then install Admin in English plugin. 

 

To make frondend arabic and backend english continue with below steps

Add languages folder form arabic version to english version

Also see

http://www.hussainhusain.com/2011/08/switch-current-installation-english-wordpress-arabic/