Go to www.trianglemtb.com
, look up the Sanford area trails. Governors Creek will be the closest, I'm guessing 45 minutes from F-nam. You're also within an hour (I think?) of Uwharrie National Forest, which has some good XC Trails IMO.
Hefner Trails are located in Fayetteville, but I'm not sure of the status of them, ie: not sure if they are legal, or if you risk trouble for riding them.
Check out Smith Lake Trails, also near the area..
If you're willing to drive a little further, there are great trails up in Raleigh, Durham and Chapel Hill. Post on the site mentioned above, an you can get more localized info.
When will you be in town, when do you want to ride, and what is your riding style?