The Mexico defender joined Porto from Club America in 2013, but has yet to establish himself in the first team at the Estadio do Dragao
Mexico defender Diego Reyes is set to join international teammate Carlos Vela at Real Sociedad for the 2015-16 season.
The La Liga club announced it has agreed on a season-long loan for the Porto defender, with the deal to be completed after the Gold Cup
A statement from Real Sociedad read: "Real Sociedad has reached a preliminary agreement with FC Porto and Diego Reyes for the Mexican player to play on loan next season at Real Sociead.