I would recommend at least 6 months. Thats just me though. I get sick of guys jumping into fights after 6 weeks of training thinking they are gonna rock the world.
Its really up to you. Judge how you are feeling and how well you are doing, then ask your coaches what they think. Heck talk to them next time you go in, tell them you want to fight and ask how long they think it will take to make you ready.
In the end only you can decide when you are ready.
Isshinryu Karate 2nd degree Black belt.
Neko-Ryu Goshin Jitsu 2nd degree Black belt.
Jujitsu 2nd degree Black Belt.
Isshin-Jujitsu 2nd degree Black belt.