All of the U.S. locations are now nonsmoking. Some allow smoking on balconies. Others, as turkel indicates, have other designated areas.
A number of the non-U.S. locations still allow smoking in units. As a general rule, you can determine the policy by going to Marriott.com (not the MVCI site), finding your favorite MVCI resort and clicking on the "About This Hotel" link on the left side of the page. If nonsmoking, the first line under "Hotel Highlights" should say, "This hotel is nonsmoking".