Boy, you TI guys never miss an opportunity to pimp Jazz Flats, do you?
If you change your strings to a thinner gauge, it will loosen them up, but you'll have to have your bass set up again. This involves adjusting the truss rod (maybe), adjusting the height of the strings, and adjusting the intonation. These are all fairly easy things to do if you learn the right way to do them (
http://www.fender.com/support/basses.php has a lot of good info about setting up basses). I think every bassist should learn how to do it, and it's pretty easy and only takes a few dollars worth of tools, some of which you likely already have.