Indianapolis Pokemon Go player here.
A few items:
Cell service has always been spotty during the con; lots of people in a small space - and I've had Sprint and Verizon. Additionally, we're going to have around 70,000 people - with many of us working on eggs as well (i.e. the app will always be on when we're walking).
Also, there will be other events this weekend such as a baseball game and concerts (just on Saturday alone!).
To add to that - there is a canal nearby that will have lots of lures and draw Pokemon players there.
But, to be honest - the server crashes on the PGo app will give us intermittent breaks so the rest of humanity can access the towers. So, in this case - server issues can be a great thing!
Also, I'd recommend deciding ahead of time when your lunch and dinner breaks will be with friends and arranging to meet somewhere.
For those of you coming to Indy - WELCOME! :)