You can polymorph into yourself -- from the 9th or 10th paragraph, "You can be changed into a member of your species or even into yourself."
The spell description implies that you CAN NOT use polymorph to imitate a specific individual, making it weaker in that respect than Alter Self (one of many complaints I have with the current revision -- Polymorph Self has been turned into a combat spell. See my comments in the House Rules forum at http://www.enworld.org/messageboards/showthread.php?s=&threadid=1194 )
From the paragraph following the one just referenced: "You are effectively disguised as an average member of the new form’s race." [my emphasis]