I checked my Dreamweaver (CS4) preferences for "default documents type" and it is set to XHTML 1.0 transitional.
I tried creating another test site with Site Assist Pro wizard (Personal, artist, Cabo Sunset, default, default)
When the wizard asks for "Page Generation," I chose XHTML 1.0 Transitional.
Here are the first few lines of code created for index.html. Note there is no doctype.
<meta http-equiv="Content-Type" content="text/html; charset=utf-8" />