What is the best position to put my Air Conditioner?
This question is primarily opinion-based, since the answer depends on what makes you most comfortable.

As a person never short on opinions, I suggest this:



Put the AC in the window at (1) and leave the doors to the master bedroom and the kitchen open. Purchase an inexpensive pedestal fan like this:



and place it at (2) blowing in the direction of the arrow. Adjust the pedestal to its minimum height so the fan blows mostly through the lower half of the open door.

At night or on cool days turn off the fan and close the door.

EDIT: You could also put the AC at the other end of the house, with the fan blowing toward the master bedroom. Which is better depends on whether you need the cooling more during the times when you would be using the kitchen, or during the times when you would be using the master bedroom.

Where I live, in the late summer it remains too hot at night to sleep comfortably. Hence I would put the AC in the bedroom.