How do you handle the different regional 'slang' vs standard Slovenian?

I’m prepping for a first conversation with a native friend from Maribor, but my textbook is strictly standard Ljubljana-style Slovenian. I'm terrified that if I use high-register phrases, I'll sound robotic or formal. Should I worry about learning the local regionalisms now, or will my standard Slovenian be enough for them to understand that I'm just a beginner trying my best?