I have used faster RAM in a laptop and it will downclock to the maximum speed that the system supports. However, some systems can be picky about the RAM they will accommodate, so it's not always possible. The key point here is that Crucial says that 3200 will work in your laptop, as you can see on their page listing compatible RAM for your laptop. They guarantee it, so if it doesn't work you can return it for a refund.
I have a Latitude 5591.  it has 4GB PC2666 ram sticks.  i'm wanting to upgrade to 32GB (2x16).  i can actually get a better deal on PC3200 SODIMMs.  i'm pretty sure there's no issue in using faster RAM than the laptop requires, but want to make sure.  has anyone run PC3200 RAM in a Latitude 5000 series laptop that normally comes with PC2666 RAM?  obviously i won't be able to take advantage of the faster capabilities of the RAM, but want to confirm that it would be backwards compatible.  
RAM speed in a 5591