I agree with BB. I would get an advert right.
One reason is that, in most walks of business/life, the most desirable buyers are educated people who definitely do spot bad grammar and judge it accordingly. That's why when you are starting a business, setting up a very clean corporate image helps dramatically in selecting a high quality customer base. If your promotional material is badly written, you have cut off both of your legs before you even started, and the only customers you will pick up will be people who are similarly illiterate, and most of them will be poor businessmen, with all the problems which follow from that (credit control, for starters
).
Incidentally, how can you tell dyslexia rather than just somebody who cannot write (a serious Q)?