he's right about the Vortex, and Little Five is crowded with people walking place to place. The record store, while small, is seemingly the main attraction. I don't see what's so great about Little Five. During the day it's lively but still rather grimy. It's also rather small and would take about 20 minutes to walk around the whole place.I much prefer Downtown Decatur near Emory University. There's a burger place called Farm Burger(healthy fresh shit) that you can stop in. There's a bison burger place around there too, but i'm not eating Bison meat, shits gross. The Georgia Aquarium was the largest when it opened in '05 so that is always neat to check out.
If you want decent food cheap I'd check Jacks Pizza and Victory Sandwich Shop. They are both near Five Points in an area called Inman Park/Old Fourth Ward. I live there. Both places have decent vibes where you can chill with a friend and talk, and possibly meet people. But don't meet the bartender/server girls at Victory, I date one of them and I lurk around the corners to make sure out-of-towners don't swoop in.
I believe I'm seeing Three Days Grace(go canada) that weekend at the Masquerade, which isn't far from any of the places I listed. There's always a decent band playing every week somewhere.
Finally if all else fails, park somewhere at the south end of midtown atlanta and walk North on Peachtree Street. I don't know your scene but there's some nice places in Buckhead, I was at a bar with a rooftop pool, but that's me.
I don't know if you're going by yourself, or with a friend, girlfriend, etc. I could name places more tailored to your party and style.
But everything listed above is for the AP.net crowd