Columbus is a major US city, with ~ 1 million people in its core and ~ 2 million in its metropolitan area. It has a wide variety of attractions but is much less expensive than Los Angeles and New York. It is central, within one day's drive of about half the population of the US. Columbus is easily and affordably reachable by air; further, there are many other nearby institutions that one could visit on the same trip. The summer weather is pleasant and the culture is friendly.
There are many things to do in Columbus. Popular attractions include the Columbus Zoo and Aquarium and COSI (Center of Science and Industry), one of the best science museums in the US. The lively Short North area, located walking-distance away from the conference venues and hotel area, is home to the city's nightlife and many of its most popular restaurants.
Columbus is one of the most LGBT-friendly US cities. You can find more information here.
Image copyrights belong to COSI, Columbus Zoo.