Going to Disney Orlando in May 2011 any money saving tips? where to stay? what to eat?

Hi me and boyfriend are looking to go to Disney in May 2011.
We will both be 21, so as far as i know we wont be able to hire a car since we are from the UK?
So what is the best thing to do?
Is it very expensive to stay/shop/eat if we stay within Disney?
Is staying in disney hotels our only option if we dont have transport? or could we stay on international drive?
Without a car will we be able to get to supermarkets and malls?
Can we cook in or will we have to eat out?

What is the cheapest places to stay that are still nice?
Where should we buy our park tickets?

Any tips you can give us would be brilliant!

Thanks