Have you tried playing with the xml file? I think this line refers to the text 'Drag to unlock' that you want to remove.Notice its start at x=0 and width is 720 which is the screen width, position at y=1100 which is the text y position and align center. If you wish to test whether its the correct one or not, just change the align parameter.
<text x="0" y="1100" w="720" h="80" align="center" size="18" color="#FFFFFFFF" src="system.unlocktip"/>
While the lines after that containing y="1105" refers to the animated arrows if you wish to remove that as well.
The xml file is at Taste/unlock/layout-hdpi/layout_taste.xml