Strangely, Holmes has never mentioned choosing the particular theater for that reason and we have his diary that details his plans for the shooting and there is no mention of that aspect either. Instead, he appears to have chosen the particular theater based on its layout and exits.
As you say, "appears". It appears to others differently:
"So why did the killer pick the Cinemark theater? You might think that it was the one closest to the killer’s apartment. Or, that it was the one with the largest audience.
Yet, neither explanation is right. Instead, out of all the movie theaters within 20 minutes of his apartment showing the new Batman movie that night, it was the only one where guns were banned. In Colorado, individuals with permits can carry concealed handgun in most malls, stores, movie theaters, and restaurants. But private businesses can determine whether permit holders can carry guns on their private property.
Most movie theaters allow permit holders carrying guns. But the Cinemark movie theater was the only one with a sign posted at the theater’s entrance.
A simple web search and some telephone calls reveal how easily one can find out how Cinemark compared to other movie theaters. According to mapquest.com and movies.com, there were seven movie theaters showing "The Dark Knight Rises" on July 20th within 20 minutes of the killer’s apartment at 1690 Paris St, Aurora, Colorado. At 4 miles and an 8-minute car ride, the Cinemark’s Century Theater wasn't the closest. Another theater was only 1.2 miles (3 minutes) away."
It's all conjecture when you're dealing with the insane.
As for Mother Jones debunking the gun free zone theory, they cite 5 pages detailing his plans
after choosing the theater. There is nothing offered in their combing of his journal to speak to what thought process went into the choosing of the theater, only the plans made once that theater was chosen.