I usually just ignore those kinds BS signs and go about my business.
IF I were told to leave because they somehow found out I was conceal carrying, I would just quietly and politely leave asap to avoid a trespassing charge..
The problem is that Allen is a middle class or better community in the northern Dallas suburbs. It is likely many of the shoppers own guns, even concealable ones, but at home or maybe in their car. They are under the impression that they are safe because they live in an affluent area, more so than people may have in South Dallas or an exurban or rural area.
Yep, that’s how I do it too. If your weapon is properly concealed, the management will never know you’re armed, and you can’t be charged with trespassing if you leave promptly when requested.