Yes, you can use Acrobat 11 to enable XFA forms. In Acrobat 11 the menu item is: File > Save as Other > Reader Extended PDF > Enable More Tools
Also, you may have heard that Reader 11 is able to save a filled-in form, comment, etc. even though the document is not Reader-enabled. This applies to non-XFA PDFs, so you still need to enable forms created with LiveCycle Designer if you need Reader users to save them.