For everyday washing...sure; however, if yours is a bit dingy or has some
spots, there are several special fabric cleaners and usually a follow up
treatment with a water repellent.  There are several brands, generally
carried by all the major parts suppliers...and even your local auto parts
stores.

Here's a link to an article that I found regarding convertible top care.
 It has links to different products that are applicable.

http://www.carcareonline.com/viewarticle.aspx?art=3