What version of Dreamweaver are you using? I can't speak for versions newer than 4.0, but Dreamweaver does not support GUI CSS layouts, meaning that a CSS layout using DIV tags will not render in DW the way it would in a browser.
I don't know, maybe MX would. The best way to find out is to go to http://www.alistapart.com/ which uses a CSS layout, and save the home page complete with the files. Don't save it as an archive file (M$ IE only). Then open the HTML file in DW MX. If it looks like in DW like it does in a browser, then DW MX probably supports enough CSS to create a CSS layout.
Honestly, the best way right now is to learn CSS yourself and write the HTML by hand. I don't know of any point-and-click website-building tools that support CSS layouts. Here's a couple references:
Pretty good for beginners
Excellent for those with good to excellent knowledge of CSS, tackles many real-world problems and shows you solutions
The official World Wide Web Consortium CSS 2.0 specs. They are harder to digest because they aren't tutorial-based.