Click here: http://trails.firstworks.com/trails/trails.cgi/default/city.html?city_id=14
Click "show on map" then zoom in and drag the map around, or follow the links. You'll find tons of trails to ride.
Unfortunately, in the immediate vicinity of Helen, most of the stuff to ride is either forest roads, like the upper Chattahoochee Loop, or expert level, like the Hickory Nut Trail.
I imagine that Stonewall and the White Twister
are less than an hour from Helen.
are great too though, and definitely worth riding.
There are some fun forest road routes up there, if you're into that sort of thing.
The Upper Chattahoochee loop is climbing up on FS44 up and descending back down on FS178. It's not too treacherous or too tough of a climb.
On the other side of the ridge by Lake Burton, an out-and-back on FS26-1 (Wildcat Creek Road) is really scenic.
Riding out on FS70 to the wilderness area boundary and back is also really scenic.
FS54 to FS54A to FS198 and then back down FS54 is also pretty nice. FS198 is barely even a road anymore.
If you don't mind some pavement and a longer ride, a counter-clockwise loop on Hwy 197, Popcorn Road, FS163, Hwy 76 and FS164 is great too. Especially the descent back down 164, though there are a million creek crossings so you'll probably get your feet wet. FS164 isn't marked at the top though, so you may have to search for it. It starts at the end of a highway barrier, near a mile-marker.
You'll need to search the site and print out maps for most of those, they're not commonly ridden.