So far OpenMRS looks good, but still just a bit too raw, unless you get implementation help. Very active development with trial implementation in many parts of the world including one in Argentina. Software has broad and professional support. Check back in 6 months. http://openmrs.org/wiki/OpenMRS
FreeMed also looks promising with multiple language support. It is available at:
http://www.freemedsoftware.org/ Site states,
"FreeMED is oldest and most sophisticated open source Practice Management & EMR (electronic medical record) product available. To date, Sourceforge.net reports over 81,000 total downloads. FreeMED is being successfully implemented in a number of clinical settings around the world including large government hospitals to small private practices."
XChart seems to be a dead project with limited to no movement and limited initial investment.
Initial assessment: There are at least a few seemingly good quality open source options worth evaluating in a more formal way.