yes , you can used your brushes for Elements 11
Put them to C:\Users\[username]\AppData\Roaming\Adobe\Photoshop Elements\11.0\Presets\Brushes folder , so that they automatically loaded on the next launch.
Use the new enhanced Edit->Preset Manager to add brushes, effects, styles and host of other things via this dialog box.
Choose Brushes in Preset type and Click on Add and choose your .abr file and it will be added in your brush library.
For more help on this complete topic view http://help.adobe.com/en_US/photoshopelements/using/WS287f927bd30d4b1f 71abaa0b12e28aec742-7fd2.html#WS287f927bd30d4b1f71abaa0b12e28aec742-7f ce
Hope it helps.
No, not all of the .abr brushes files will work in photoshop elements 11.
Depending on the type of brushes used in the file and if they were saved from photoshop cs6 or photoshop cs5
you will either get a message that the file is not compatible or certain ones will load, but when you try to use the brush, photoshop
elements 11 will crash.
If the brush files were saved from photoshop cs4 or older photoshop versions, then they should work.