>>42538035
I can understand anons in voice calls just fine, so i assume that translates to irl just as well. Instead, i think the biggest barrier for me would be talking and actually being understood by the people at the con.
You're probably in the same boat as me where listening and reading is much more commonplace than speaking, so make sure to train both! I'm considering taking classes just to iron out my speech before going.
If all else fails, you could also try to befriend other ESLs at the con. I've found that we have an easier time understanding each other than natives would, and there is much less pressure when the guy you're talking to is just as bad.