Ok, as someone who has worked on Otay for about 2 decades,
, as of 2 days ago, the fire restrictions ended, and it is ok to target shoot on BLM land there. I DO NOT work for BLM, but am passing along info that was given to us, letting us know people are allowed to target shoot there again. And don't be offended at anyone asking you to clean up, they are not accusing you, they just have seen what is left out there. I could take 100 photos today for you and show you the trash that has been left out there. We are our own worst enemy, unfortunately.
There are a few spots that are commonly used. One person mentioned earlier the east side. Go down Marron valley Rd., just past the gun club, then head up the truck trail. First road to your left is Ridge Road. Most of this is BLM, you will see where they shoot. Other choice is behind George Bailey detention center. if you have a good enough vehicle, you can go back in there and there is a place everyone shoots. A few target stands are placed on the hillside back in there, it's a pretty decent spot.
There are a few more areas, but those are probably best.