Cultivation gives an intial boost to fertility but destroys beneficial earthworms and soil structure as well as turning up buried seeds which germinate. Besides, the 'weeds' you mention could form the foundation of a balanced eco-system to support your food plants. Seeing 'getting rid of the weeds' as your first priority is the 'agriculture' paradigm. Your first step should be to plan the garden to conserve water - this summer serves as a warning. Before you start digging you might want to read Bill Mollisons 'Permaculture One and Two', Masanobu Fukuokas 'One Straw Revolution', Toby Hemenways 'Gaias Garden' or Sepp Holzers 'Permaculture'. Youtube these four permaculture pioneers for an instant insight into how water management, weeds, chickens and perennial crops can increase your yield and reduce your work load. Remember that your 'community' may not be as dependable as you hope - especially when you ask them to dig.