How are you getting the "Leon Target"? Also, are you keeping on moving the region to self?
In the event for my main character, I simply set that as the attriubte for him. I was hoping it would make things easier but it doesn't seem to work. Also, I made sure it was moving and got that to work thanks to Ozy's and your advice below...
As a quick follow-up to Ozy's comment, for the creation and movement, if you want the region centered around the player, the fastest way to do it is to use:
create region at x: [x-center of self - (half of the width of the region)], y: [y-center of self - (half of the height of the region)]
Use the same idea for the movement coding. Then you don't have to play with the numbers
Upon turning on debug drawing, from what I see, your idea worked very well, thank you!
First things first, you're going to want to enable debug drawing whenever your code involves regions, as it makes them visible (saving you a lot of irritation and heartache when debugging).
That is very helpful, thanks! Now I can see the movement of the region, so I know what's going on and am not completely in the dark.
Your region box is waaaaay too big. When I punched in your specifications it reached far around and below the enemy into the abyss. Try and position it so the actor stands at the very center of the region. You'll have to play around with the numbers a bit, but for me the optimal height and width was 30 and 150, respectively (a side note, I was using the default Prolonger sprite when programming this so yours will likely require a different size). Try and think in terms of x-position and actor width because the origin of the region is often contrary to what you'd expect
If we assume that your enemies will be moving (which they probably are), another problem that occurred with your code is that the regions don't follow the actors - they stay fixed at the exact point you created them. Needless to say, you don't want this. You can add an "Always" event that constantly realigns the region with its actor using the "make region follow" block.
I've fixed this recently, and everything is in working order except for one problem. Once the enemy has gone past the player (Within the region), it continues to move, even though it should be changing direction in response to the player being on the opposite side of him. It only changes direction when I leave the region and then return...
I figure this is because the event I'm using to trigger this is not constantly being updated? I'm using the "Enters region" event to trigger the movement instead because when I use "Updated", the game stops working and the flash player freezes. I'm guessing this is because always checking for the movement inside the region is simply too much... so any ideas guys? The code is very close to being completed, it's just that one little problem that remains.
I appreciate all the help so far, by the way.

Below is the code I now have.