You don't need to separate the ball joint, the strut would be easier to pop out IMO. You don't have to drop the sub-frame, you can use a floor jack and a short piece of 2X4 and jack up on the strut plate, while the mount is still secured to the strut tower. This will compress the strut up enough to come out of the steering knuckle.
**NOTE: There are people that will advise against doing this, and for good reason. When jacking with the piece of 2X4, you chance it kicking out, which could result in injury. Either way though you can do it this way or drop part of the sub-frame.
I was able to replace the passenger side front wheel bearing on my 2004 Taurus without separating the knuckle from either the lower control arm or the strut. Getting at the three bolts that hold the bearing in place is awkward, but it can be done.