I was hoping to find the above in this forum... Instead, I was only greeted with "If you don't want that to show up, do not use galleries"
Not really the answer that I was looking for since I wanted my page to display as a gallery.
So knowing that the entire source is open and editable, I went searching for the little piece of code that displays that annoying one line....
If you want to remove it, here are the simple instructions:
Go to Appearance => Editor
Look for the file called 'content-gallery.php'
Next search for, and either comment out or delete the following code:
<p><em><?php printf( _n( 'This gallery contains <a>%2$s photo</a>.', 'This gallery contains <a>%2$s photos</a>.', $total_images, 'twentyeleven' ),<br />
'href="' . esc_url( get_permalink() ) . '" title="' . sprintf( esc_attr__( 'Permalink to %s', 'twentyeleven' ), the_title_attribute( 'echo=0' ) ) . '" rel="bookmark"',<br />
number_format_i18n( $total_images )<br />
Press 'Update File' on the bottom, and your reference to the images should be gone.
Hope that this helps.