drupal 7.12 : multiple taxonomy vocabularies in a single view exposed filter One of my colleagues is working on a project for a departmental store. she wants to create a single views taxonomy drop down filter with multiple (7) vocabularies. The Vocabulary name should appear in the drop down menu but should not be selectable. Some of the vocabularies and their terms are as follows.

Footwear - sandals, shoes, boots, pumps etc

Trousers - chinos, jeans, bottoms

T-shirts - polo shirts, polo neck tops etc 

Dresses - maxi, ballgown, one shoulder, tunic etc

Accessories - bags, watches etc

Questions is, is it best to use multiple vocabularies or one vocabulary with multiple parent terms and children. If she uses multiple vocabularies (e.g.. footwear, trousers, tshirts) how can she make the terms in each vocabulary appear in one filter as well as the vocabulary name (but should not be selectable). 

On the other hand, if she uses one vocabulary with multiple parent terms and their children, hood can she make the parent terms appear in the drop down menu but not selectable. she tried this method but the drop down is too long and the parent terms are selectable.

alternatively, is it possible to make the vocabulary names appear in one filter and have another filter conditionally showing the terms in the vocabulary selected in the first filter. To add to the complexity, the second filter should show the terms with products and hide those without (this is not a priority). This method will be beneficial but she has no idea how to implement this.

Any suggestions will be greatly appreciated. Thanks in advance.
I recently did the exact same thing for a client. The website is http://www.buyagainbaby.com.

You will notice there are 9 primary categories each with subcategories.  I achieved this by creating 9 different taxonomies. After researching this for weeks, I found this was the best solution. Here is how I did it.

9 taxonomies, each named for the product category you want, Footwear, Trousers, etc, then add as many terms as needed to each vocabulary. Now create one content type for each corresponding category and then assign that vocabulary to that managed fields area. At least this is how I did it.  It was a bit of a chore to get setup, but, bit was worth it. All the search functionality is done with views filters and having it architectured like that lets me do some very complicated things with filters and views.  Let me know if you have questions.  Oh one more thing, keep the content type name the same as the vocabulary name, and that will help tremendously in simplified complicated views to return products, etc.