I don't know how seriously you've meant this - but while English speakers are often very forgiving about grammary and spelling, French speakers are not. They may not tell you, but to them, bad spelling looks sloppy. If I had my own company, a supplier who sent me an offer full of spelling mistakes would probably get a thumbs-down, the idea being that if you can't even hire a secretary capable of writing properly, your products and services must be of corresponding quality.
Now, many French people know that they speak Ingleesh far worse than you write their language, so they might be forgiving