This is by Barbara Marcouiller, a lawyer in Avvo

link is here:
http://www.avvo.com/legal-answers/intenational-student-with-f1-and-granted-temporary-1664867.html

It's a bit tricky. TPS doesn't give you an actual status, but protects you from being returned to your country temporarily, and allows you to work in the U.S. in the meantime. it does not allow you to change status. Here's the tricky part. You absolutely must register for TPS during the initial authorized registration period, and then extend during the designated extension periods. EXCEPT, so long as you are maintaining lawful non-immigrant status, you will be allowed to register for TPS late (outside the initial registration period) if you apply in less than 60 days after your current status is no longer valid. So, you might think about maintaining the F-1 status in case you'd like to change to H-1B or something else later, and if not, then apply for TPS.