Can I use metal brackets to install a wood fence across an existing concrete driveway?
The only potential problem I can see is wind. I would alternate the pickets on each side of the rail. This allows the wind to pass thru the fence. This design does allow for viewing thru the fence if you are close though. Cars or pedestrians passing by would have a difficult time seeing thru it. I would drill a hole on three sides of your socket. Weld a nut over the hole. This will give you a setup similar to a Christmas tree stand. By inserting  bolts in the nuts it will allow you to adjust the post to plumb it.