Doctors do not go there for their training to return to the US, they would still need to go thru all of the foreign med school grad requirements and they are quite tough. Same thing for nursing school. Their nursing programs are in Spanish, same thing with the medical porgrams.
The only med school I know of that consistently trains US doctors is la Universidad Autonoma de Guadalajara (Autonomous University of Guadalajara). After the four years of school, these guys do have to complete a one-year 'fifth pathway' program prior to entering US residencies. They teach the first year courses primarily in English. As the students progress through the program and gain Spanish skills, more and more of the content is taught in Spanish.
As for nursing schools, if you were looking to return to the US, you'd probably want a US accredited school. If you were looking for something a little off the beaten path and knew enough Spanish, the University of Puerto Rico is a member of the AACN and has campuses in San Juan and Mayaguez, PR. However, I don't know what the cost would be like and I'm not sure if they have any English language programs.