Good for you critter garden! You have a ferral cat colony, you are not importing one. Your neighbors should be thrilled- - someone must do something.
I would approach it proactively- put a letter in people's mailboxes- the cats will suffer and die over a short life span, but not before 4,5, or even 6 litters, all of whom will potty in soft soil of veggie gardens and flower beds, killing birds at bird feeders, carrying communicable disease (you could raise the rabies flag is you have a neighbor who's a real jerk, even though its not likely) etc. Send out a request for ideas and help; for trapping, with vet bills for neuter/spay, etc.
That way if you hear nothing they will be/should be ashamed of having a problem in their neighborhood they did nothing about and you're the proactive neighbor, not the crazy cat lady.
I don't want to see you blamed for a cat problem that fell in your lap. Turn it around and put it on them, you might not get much help, but at least you won't be blamed when you do the right thing- feeding, sterilizing, and anything else that can add compassion to their lives.
Putting out a food station can be seen as irresponsible by the uninformed, as if you put out food in the hopes of attracting a colony- but notifying your neighbors there is a feral cat problem AND putting out a food station AND work with a local TNR - that's very responsible as a neighbor and property owner and compassionate human.
Back on topic- the space under decks is not for plants. 3 hours a day of burning late day sun doesn't make any plant happy. Maybe take down the trellis, replace it with hanging plants and make yourself a nice seating area?
