ilex, I think you have the right attitude and understanding for the best possible outcome...over the long haul.
Forgot to mention..... with one strand of barb wire (rather than two), it can only get tangled up with brush. If you have two, they will get tangled together.
There is a magic height for a single wire... just high enough to make people worry about stepping over it (Spaniards are a little shorter on average than Anglos, thus this point is a little lower to the ground). Getting crotch caught with an electric barb wire is certainly something to remember. Don't ask me how I KNOW

This same height is low enough that a person MUST lay flat on the ground to roll under it.
I have been to Spain. I know that cactus is native there... you can scatter/plant prickly pear cactus right under and along the fence line.... over time, it should grow together and form a better barrier than a hedge... and all you have to do to fix holes in the barrier is to break off a pad and place it in the open space...give it a year...there will be no hole there

It is cheap, too, planting is easy, what is not to like about it as a barrier. And, it is native
I like your attitude of not mixing it up with 50 people with knives..... but all of them will pause and consider avoidance measures when approached by a shotgun-wielding, shooting-in-the-air, crazy acting fellow pulling grass, examining it carefully, then tossing it in the air and exclaiming,
"GRACIAS A DIOS, ESTE ES MI TIERRA, ES EL MUNDO MIO, NADIE SE MOLESTO!" Punctuate this with a shot when you know you are being observed and wish to emphasize your attitude
For added effect, and to insure communications, you can variously use Catalan, Spanish, Portuguese, English and whatever other languages/idioms you may know. Come to think of it, this can be accompanied with your own version of the Maori War Chant.
http://www.bloodandmud.com/2008/11/rugby-video-mao.html
Best wishes...oh, yes, when your war dance is perfected, please post for us to see
