The only BBQ place in Cary is "Danny's Bar-B-Que" (311 Ashville Ave # G, Cary, 27518 - (919) 851-5541).
Danny's chopped pork Q is very moist and chunky, with only a slight smoky flavor. It is not sauced at all. I rated this Q as average (2.5 on a 1-5 scale).
There are only two other Q-Joints in the area immediately around Cary: Dixie Bells Bar BQ (1241 Laura Village Rd, Apex, NC (919) 303-6676); and: Ole Time Barbecue (6309 Hillsborough St, Raleigh, NC (919) 859-2544).
Dixie Bells has pulled Q that is a bit dry and chewy. The only flavor is a smoky taste that I think is artificial. It is average in grade (2.5), but is a little high in cost.
Ole Time Barbecue is pretty good and is fairly close to Cary even though it has a Raleigh address. This Q is a bit better than the others (3), and usually has pretty good flavor although you may find it a wee bit dry.
If you want GOOD BBQ, I would recommend that you head into downtown Raleigh to "Clyde Coopers BBQ" (4.5) or to a "Smithfield's Chicken & BBQ" (4.7), a chain with numerous stores around the area (not in Cary).