Only if the property is posted. If it's just some crap in an employee handbook, it's not breaking the law. It might be a bad business move to carry there, but it's not breaking any law.
Anywho...back to ankle carry. I'm not so sure that ankle is a big improvement over IWB when driving. I did some practice drawing with mine and found that the steering wheel is really in the way when trying to use my left hand to pull up my pants leg to expose the gun, leaning forward, and drawing with my right hand. I have long legs, so maybe that won't apply to everyone.
It's definitely not my first choice in ways to carry. It's a little more awkward having the weight at my ankle instead of my waist, it takes longer to draw, and I'm much more self-conscious when using the ankle holster. Still, I'm glad I have the option when IWB/OWB/AK-47-across-the-back isn't feasible.