I spoke to a technical writing professor here at OSU. When I first came back to school I wanted to go into tech writing, but with all the outsourcing and temp contracting I wanted a little more stability.
My instructor has long noticed that there is no pattern to which of her students have a good grasp of grammar and who doesn’t. Personal and cultural background seems to be irrelevant. Regardless of comprehension, she is not bothered by students’ lack of grammar skills. At this point the basics should be largely taken care of, and she feels that if an instructor gets extremely bothered by such things it would interfere with his or her enjoyment of the teaching profession at large.
Writing styles and grammatical usage have grown more informal over the years, perhaps largely due to the proliferation of e-mail. Most of the outright mistakes seem to be sentence fragments and inconsistencies in the writer’s point of view.
The instructor has worked as a consultant for many tech organizations and states that a lack of grammatical skill doesn’t necessarily hold someone back in the tech writing field so much as mastery of these skills helps them move ahead and excel.