You could probably get credit for the tires, but I found they don't have enough demand for them, so you're probably better off keeping them. I did. Besides, the tubes are the same for 28 and 32, so you've got that going for you. There are some good tire deals online, too. Search the forums for a couple favorite commuter tires like Schwalbe Marathon and Continental Gatorskins.

I'm sure you'll get other suggestions, as well.