The life cycle of the olive fly is interesting. The fly lays eggs in the olive leaving a little scar. If you look at your olives on the trees and see most of them scarred then you know what to look forward to.
When the olive falls to the ground, the grub leaves the olive and burrows into the ground. The new adult fly emerges eventually from the ground.
The only way to keep the flies from reproducing is to clear all olives from the trees and collect any on the ground in the hope the grub hasn't already left. If your land is clean then you might a thorough raking under the trees during the winter.

My personal experience of trying to stop them reproducing has been abject failure. Our land isn't clean so olives drop everywhere. If next doors land isn't clean then you will get their flies anyway.

The other approach, capturing and killing flies has been much more successful. We use the plastic dome traps and bait them with some meat & water. It takes a few days to go off and make a good stink and then the flies home in. Sufficient traps (we use 4) carefully placed about 30 feet from the patio keep all but a very few away from us. The totally gross thing is.... Once the traps are in full production, we just empty about 3/4 of the dead flies out into a plastic bag, top up the water and carry on. It seems that dead flies are the best attractant.

Anyone looking for bulk supplies of netting might try these guys in the US. They shipped to me in the UK for $47.63 paid by Paypal.
http://www.chiarmy.com/IBS/SimpleCat/Product/asp/product-id/672385.html

Finally, my pal tells me that the flies hate Chlorine. He keeps his pool well topped up and the area is completely clear. Anyone else found this?