Maybe neither of us understands the question, or maybe its too basic? Thats not meant as an insult to who asked it; just an observation by one, who is also about ready to sign on with Dreamhost, and had the same question, too. (Well, sorta!)
Thing is I come to this arena with only a rudimentary understanding of the skills needed to create an entire website. However I understand the need (or desire) to place something in advance on the internet - as a way to generate buzz or just make the target audience aware of whats coming.
That said, if one were using, say, Wordpress.org development tools, can an interim (single "Coming Soon" page) be created therein, and vis a vis Dreamhost (but not yet as an actual website, but using their hosting services), that may/could have the capability of having visitors "sign up" (so to be part of the official launch)?