That depends on your overall goals in fencing. Do you want to become a world ranked competitor, while starting at 28? Or do you simply want to pursue it as a hobby? I would actually like to get into Kendo and I am looking for dojos that teach it. I am 32, four years your senior, but won't age restrict myself from it. I hope it works out for you.

Yes, why not? But it might take longer time than if you were, say, 14 years old.