I live in Gwinnett (Duluth) and there are plenty of great rides from my front door. My favorite is a 50-mile ride to Lake Lanier and back, which passes through Suwanee and Buford. There are also 3 very nice multi-use greenways in Gwinnett, about 10 miles each. I prefer the secondary roads so I don't have to dodge strollers. ;-)

Check out out the Strava heat maps, they'll show the most heavily travelled roads by bike. I use this to create my routes.