May get lots of differing advice on this one.
My opinion, FWIW:
If you are unwell below the neck, i.e. fever, muscle aches, cough etc then DON'T run until you're better.
If it just the throat and all above the neck then do the race as a training run, but don't race.
Organised training runs are fun. You get the measured course, lots of company and drink stops - drink plenty. Trot round at training pace and enjoy it. You'll probably find some other people training for a half as well.
GL with the training