From my experience, you absolutely do not have to be good at chemistry to get into biotech. There are so many disciplines that fall into the field of "biotech" that you won't necessarily need to call on your undergrad chemistry skills. I think it will help if you really want to gain an understanding into what you are doing though. Chem, biochem and O -chem all teach you a lot about how just about every biologic process works. Good Luck!