Just enjoy the experience, chances are Jon will up his game on the bigger stages for South America, and even if he doesn't just enjoy the songs anyway. The band is tight and you'll be too busy in the moment to really concentrate on Jon's voice, it'll only be after the fact that you'll watch videos and realized he sucked singing this or that and "hey yeah, I remember that note, he nailed that one but the other 100 not so much"....