PENAS BLANCAS, Costa Rica — As summer began to bake the central Cuban city of Sancti Spiritus, Elio Alvarez and Lideisy Hernandez sold their tiny apartment and everything in it for $5,000 and joined the largest migration from their homeland in decades.

Buying two smartphones for $160 apiece on a layover on their way to Ecuador, they plugged themselves into a highly organized, well-funded and increasingly successful homebrewed effort to make human traffickers obsolete by using smartphones and messaging apps on much of the 3,400-mile (5,500-kilometer) overland journey that’s become Cubans’ main route to the U.S.

Some 45,000 Cubans are expected to move by bus, boat, taxi and on foot from Ecuador and other South and Central American countries to the Texas and California borders this year, afraid that the normalization of relations between the U.S. and Cuba will mean an imminent end to special immigration privileges that date to the opening of the Cold War. With thousands more taking rafts across the Florida Straits, 2015 may witness the biggest outflow of Cubans since the 1980 Mariel boatlift that hauled 125,000 people across the Florida Straits.