I second capital ale house. Very good place to go before the show, because of the very nice beer selection (if only it were monday for dollar burger night, it'd be heaven). I also second the notion that there is a whole lot of good food in the area.
However, if you're going to go anywhere further than that, tobacco company et al, you're probably gonna wanna drive (it's only a few blocks, but still, why walk when you can drive and it's easy.. unless you've been drinking).. and if you're going to drive. You need to make your way to the bottom to 17th and Dock street and go to Bottom's Up Pizza. Soooo good. Of if you're in the mood for generic bar food, there's a BW3's right down there too.
It's really not far away, Total of 13 or so blocks from the club.
Anyway, once you're in the bottom, it's not too rough to get back to the National.. just make your way up Main Street for about 10 blocks to 7th and then find somewhere to park. Anywhere between there and Broad street, anywhere on (9th, 8th, 7th running north/south and Grace, Franklin or Main running East/west) is only a one-two block walk to the club and is free street parking.