The way the law reads in Florida, it looks to me like if you pull (i.e., show) your gun in an attempt to deter a crime in progress, you are not brandishing.
The problem is that it has to be a crime in progress. So when you pull the gun, you may stop the crime from progressing. If you do that before any evidence is created of the crime you stopped ever happening, then it's your word against the criminal's. And now he's seen your gun and can describe it.
So, if there's not already damage or some kind of evidence already, you can't get away with pulling your gun until you HAVE to shoot.
If you are about to walk into the parking lot and see something suspicious but not clearly criminal going on, you'd be a fool to pull your gun out. But there's nothing wrong with giving the grip a little tug to loosen it in your holster, or clicking the safety off, or whatever might make drawing faster for you. At the same time, this sends the message that there might be something right there for you to use against the bad guy, which he does not want, without enabling him to describe your gun.
If this were me, and I saw anything that was clearly not right or I just had a "bad feeling" (see below), my first act would NOT be to just get my gun ready and stomp out into the parking lot. I would probably wait until several other people were also moving into the lot and then go at the same time. I would do as described above, to hint to any miscreants that I am armed, so that if he's determined, he'll pick another of those other people as his target rather than me.
Now, if you are trying to say that there are signs that somebody in or near the parking lot is fixated on YOU as a target, well, that doesn't change the legalities of when you can defend yourself with deadly force. You are faced with knowingly stepping into a situation you strongly think is dangerous but has not yet turned threatening to life and limb.
The problem with that is the bad guy, in this case, is ready to go. You are not, and cannot act as quickly as he can. In this case, I would go back inside and see whether I could figure out a safe way to reach my car. Is there a security guard? Will the manager walk out with you? This might make you feel like a wus, but what do you like better, that or death/serious injury by a criminal because you put yourself where you couldn't react fast enough, or life in prison because you reacted too fast?
For methods of dealing with that "bad feeling", see The Gift of Fear by Gavin deBecker.