You know who owns the place?
Talk to the owner & see if he/she's keen for you to keep using it after a group of you clean it up. Get a local shop to supply rubbish bags for people to take their trash home after they've been there.
Do something about it if you can, don't just bitch that others don't care.
If the owner's not receptive, it's been worth a shot. The best idea is to give a **** while the land's open & keep the landowner happy.
Just see if you can do something.
Good luck & let us know how it goes - it look awesome :)
(disclaimer: this post is made with the limited information supplied lol - but seriously, see what you can do).
Michelle