Hey TSevs, if you're talking about the Foster Ave bridge over the NSC, I haven't had any problems there. But then again, I've only fished that spot a couple of times.
If you're talking about the west bank area with the partially submerged rocks that's just northeast of the foster dam, hehind the southeast corner of the athletic field, I'm pretty sure that spot is fine too. In fact, I ran into my first ever DNR (CCFP?) cop there a couple weeks ago. He stopped by to ask for my fishing license and was very polite about it. Also, I sometimes see chicago police slowly crusing by in their patrol cars. Even when they've stopped on the walkway by the fence (with the railing) and are just looking around, they've never given me any problems.
I guess the rule of thumb is to keep a low profile (i.e., don't throw beer bottles in the river or holler really loudly) and you should be OK fishing this area. Good luck