I can't think of any within walking distance offhand, but you ARE within walking distance of a MARTA train station if you need to go a bit further out.
Well, googling turned up a few but I can't vouch for them. You may want to call them before you head out of your hotel as I have no idea if they're still there or not.
Closest one I've found to you so far is:
Calabash Vegetarian Kitchen
233 Mitchell St SW, Atlanta, Georgia (30303) (at between Spring & Forsyth)
If you want to list the other ones I can tell you where they are in relation to where you'll be staying and the easiest way to get to them if you'd like.