Hi Shirley

This is a bit more natural to use in Spanish, to be honest, "hablar discretamente" would imply to talk in a way where they are conscious that they might be overheard, so this may also mean that they speak quietly. So you can imagine someone talking "discreetly" when they try to be cautious so others don't overheard the conversation. I hope this makes sense.

Saludos

Inma