Help with Garden Maintenance

I have a back yard that has been unkept for several months. The grass has turned into tall weeds and the weeds have grown into tall weed trees. The space is about 20' X 25' with a walkway that extends about 40 feet (width of walkway half 3' second half 5'). I want the whole area cleared out down to the ground, the growth placed in garden bags and left in my alley for pick up by the city and any incidental other materials placed in our garbage cans.