I was going to write a long discourse about this, but others have already done so, and given good ideas of how to stay safe.
I have traveled to over 100 countries, most of them more than once, and quite a few dozens of times. I had my passport taken out of my pouch in the Netherlands (it was in a leather container and they probably thought it was my wallet), someone tried to pick my pocket in Costa Rica (I felt it and stopped them, but they got away).
I have traveled to the famous favelas of Rio de Janeiro and while there may be areas that have gangs and guns, what I found was just people that did not have much money and needed a break.
Curitiba is, in my opinion, relatively safe if you follow some of the guidelines that people have given here.
I might add that while marriage equality is the law in Brazil, and Curitiba is a relatively tolerant city, there is still a strong homophobia shown by some groups, so same-sex couples may want to be somewhat discrete.
Along the same lines, in Brazil "Motels" are not just a horizontal "Hotel" like in the USA. "Motels" are places where you can be very discrete with your partner (either opposite-sex or same-sex), and rent a very nice room for short periods of time (like three or four hours). "Hotels" are what you find in other countries.
Stay away from political arguments. Brazil has just gone through a very rough political election, and people are still touchy about it. Polite discussion of political topics are probably ok at Deb* itself, but wearing political pieces of clothing (even historical political figures) may cause more than conversation afterwards.
Holding your very expensive Samsung or Pixel 3 XL up at any event to take a picture may find your camera snatched out of your hand.
Finally, there are lots of other things to see in Brazil, and if you have the time and money you may want to add a couple of extra days to see areas like Foz do Iguassu, or Florianopolis. But I am sure the organizers will tell you about them.
Looking forward to seeing you all in Curitiba.
maddog