I would be REALLY careful about buying a clearance lens at Walmart... A lot of times they are 'open-box' lenses, which means every 3 year old that has seen it has stuck his fingers inside and bounced it around.
On Target.com you should be able to get the 75-300mm for about $200. Try to track down a discount code online and you should be able to get about 10% off. That will at least cover your taxes and maybe your shipping. At least that way you know it will be new, and you can return it if it's screwed up.
A lot of people will say that it's crap, but if you are shopping Walmar clearance for equipment (kinda like I was) you will probably be thrilled with the quality... at least for a while. It really is nice to have the reach of the 300mm. If nothing else, it isn't TOO expensive, and it will be nice to have from time to time. Then you'll turn into me, and start wanting BIG L zooms... hehe