The U.S.-Mexico border is currently patrolled by 10 Predator surveillance drones. The immigration reform bill introduced in the Senate would increase that in order to provide constant coverage. ABC/Univision reported 
“Unmanned aerial vehicles, or drones, could soon be patrolling the United States border with Mexico 24 hours a day, seven days a week. That's what the major immigration reform bill introduced last week by a bipartisan group of senators proposes.
“The goal: "effective control" of the border. Under the bill, no immigrant granted provisional legal status would be eligible to apply for a Green Card until the Department of Homeland Security shows it's made substantial progress toward that goal. Border hawks want the pathway to citizenship more firmly tied to border security success.”
But, as Common Dreams reports ,
“As the new immigration reform bill moving through the US Senate puts aerial drones at the center of a beefed-up militarized approach to border security, a new report shows that the existing drone-border program has proved an "inefficient, costly and absurd approach" to monitoring the border or enforcing current immigration laws.”
The report was produced by the Center for International Policy, you can read it at Drones over the Homeland .