Camera Help

In my opinion I would not spend the money to put cameras up in an already problematic area. These people that are drinking there just might find your cameras and steal them.
Even if you did capture photos of persons drinking, I doubt that law enforcement would do anything regarding that problem.
Post that area with numerous signs high enough that they can't be torn down and continue your regular patrols of that area.
In my county the prosecutors don't like filing a trespassing charge unless another crime occurred
such as hunting or fishing without permission.
If you search the trash that has been dumped and you locate items with names and addresses such as mail, then contact a law enforcement officer and ask that they meet you at that location, then show them the items you located.
Let them remove the evidence you found it makes for a better case.
You might also want to photograph the stuff that is being dumped so if an arrest is made you can show the court the continuing problems you have had with that location.
If you pay someone to haul trash away keep the receipt,the Judge may order the person arrested to pay you for the clean up.
Good Luck.