See if you can borrow a few goats from someone you know.
My sister has goats, I just go and get 3 of hers and let them graze with the horses for a couple of weeks. They prefer the weeds and the horses prefer the grass. When everything looks better, I just load them up and take them back home.
Its a win win for me and my sister, I get the weeds gone and she has less to feed for a couple of weeks.