The best place to grab a beer in Denver is Falling Rock Tap House. The good news this is walking distance from the convention center. They do not brew there own, but they have lots of local's on tap. They have lot's of everything on tap.
1919 Blake St.
Denver, Colorado
If you want a local brewery Downtown then check out Great Divide, also walking distance. The Oak Aged Yeti Imp. Stout is amazing.
2201 Arapahoe Street
Denver, CO 80205-2512
Or Wynkoop, the incoming Colorado Governor used to own the this place, across from Union Station and yes walking distance. I am a fan of the St. Charles ESB.
1634 18th Street
Denver, CO 80202-1212