I'm 18 and I want to get really strong, should I take HGH?

Probably not. First of all, you are probably male if you are asking this question, which means your testosterone levels are raging right now. You can get strength by a combination of a good diet and workout program. Second, your hgh levels are at their highest point they will ever be, supplementing with something that you are already at your maximum level is never a good idea. If you are trying to compete for very big competitions then you might have more of a reason to use it. But if you are already at that level you probably already know all about it and have made up your mind anyway.