Assuming they're tourists, probably ask the rental car agent and hotel clerks what the best routes to <destination> are. Most locals in hospitality in my experience are happy to share their insight with you.
The problem is like the other said, people need to be on their toes in a foreign environment. It's the same with foreign nationals visiting the US, like people visiting SF accidentally ending up in the rough areas of Oakland, or visiting tourist destinations in Mexico. At some point, personal responsibility needs to come into play, and that includes doing your homework about sketchy areas to avoid. It isn't victim blaming to ask people to think and prepare, and not go blindly wandering about.