Steve,

Wish I could go to something like this.
But it's too far and I have a day job.

I'd suggest doing
(a) a demographic map of the vendors and
(b) a demographic map of the attendees.

Many niche exhibits are better off finding in a central, accessible location
while it seems others are better off travelling.  That would be a difficult
matter to assess.

Here's thoughts on some locations:

Dallas? Easy to get to.  SW Airlines is cheap.  Good central location.

TwinCities?
KC?
Omaha?  
OKC?    Good access and often cheaper lodging than Dallas.

Columbus or Cincinnati?  No reason why not. :) Great eastern-half locations

Chicago? We can see the Cubs afterwards
Denver/Colorado Springs? Very practical western-half access.

Portland?
Seattle?  too far from anything

Atlanta?  Good for the South, but not much else.

LA?
SF?  I'd evaluate these based on demographics for the future.
    If very few (%) attendees came from outside CA/AZ/NV then they
    need re-evaluated as realted to your goals.

BTW -- What are your goals for the conference?

Just my thoughts.

Collin