I agree that you need to learn one position pretty well then move onto the next. Once you know that next position be able to connect the two positions on any string. Keep repeating this process with all the different positions. I wish I would have done this when I was first learning scales. This will make it easier to be able to play in key all over the neck!

Once you do learn all the different positions really well in one key, do not just practice in this key. Even though the positions are moveable, some find it difficult to move the positions up or down a few frets. I recommend practicing in all keys just to be more comfortable in other keys.