Amnesty International, the ACLU, LULAC, and La Raza Unida would be all over them if they set any kind of traps for them.
Unfortunately, ranchers hands are tied. There's not enough Border Patrol agents, and illegals have as many rights as we do right now.
Almost every sherrif in every border county says there is a huge problem, and it has to be stopped.
The ranchers I know are armed to the teeth. Just in case. And with the economy, many of them can't afford to keep up electric fences. 
So this is the Yankee speaking here. Put up signs that say you are digging looking for water. Caution water digging on here. So you have to dig in fifty spots you are doing nothing wrong, have advertised there may be open dry holes on the property. As long as you advertise dry wells and some one falls into the hole they are tresspassing .
Don't even have to dig these test wells, the idea that you may have done so will reroute the people from crossing your property.
Electric fences will not stop a human, they just dig under them.
About all I can think of other then that is to raise pit bulls. Head to Mexico and a thrift store and buy old shoes. Come back let the dogs get the scent of the shoes and beat the hell out of the dogs with the shoes.
Dogs will be fine with family but the first sniff of the shoes they will go in a pack out to eat up those with the smell.--- nothing like reading the Hounds of the Baskervills to give this idea.
Sorry pet lovers but when ones life depends on thinking outside the box---anything goes.
