I spend very little time down in the city but cycling the MUPs in SAT w/ friends who live there "large groups blocking the trail" are the local families living adjacent to it who are using the space as part of their neighborhood. You would most certainly not wish to provoke an altercation with them but we never feel threatened, anxious or anything other than as neighbors using and enjoying the same resource. A little respect and good manners are all that are required.
The constant fretting over "Rights" and the general Paranoia in A&S is a symptom of something deep seated and anti-social IMHO.
Have a Block Party and get over it.
That's how we roll down here.
-Bandera