Last night I rode bikes with a group of friends from Harbor island to the SD downtown water front to watch a concert for free for the first time. We had a great time watching Bonnie Raitt and Mavis Staples perform. It was my first time doing this, but my friends have done it many times before.
As you can see in the photos you can clearly see the stage and the giant jumbotron, so the concert experience far outdoes watching Humphrey's concerts from the docks.
However, my friend told me that they keep cutting down the area that people can stop and watch concerts outside the Rady Shell. There are areas just outside to the left and right of the stage, but the largest area on the open bayside used to allow people to fill up the entire outside area. Now concert goers are limited to either sitting on the rocks or in a chair directly in front of the rocks and you have to put the bikes back on the rocks as well.
I'm not sure how much longer this will even happen as well...so if you plan or this experience, do it soon.