The locomotion section says that all droids begin with the base speed as indicated by the table.
Turning while flying is a different matter. In 3.5 edition, the act of turning while flying had a cost in number of squares associated with it as seen in the Monster Manual and the Draconomicon. It appears that the PHB for SE doesn't cover that but refers you to the directions for the miniatures game involving the Battle Fleet line.
Hovering and Flying are two different types of locomotion. I would say that turning while hovering would have no cost associated with it at this point but flying would, since aerodynamics takes over and you just can't get past that in a sci-fi setting. I would reference the books I listed above. I imagine that the next source books will cover flight movement and offer some feats or modifications you can take to decrease the movement cost.
Hopefully this helps you.