So I've recently ran into a strange situation. There are workflows created with SharePoint Designer and the Workflows option is not available for some users. After doing some more investigating I found that for certain sites in a site collection, only the Site Collection Administrator could even see the previously created workflows or add new workflows.
The inheritance on the site has been broken and fractioned all throughout the site. I haven't found a link to the SharePoint Designer workflow permissions through the SharePoint Site directly, but I have found a workaround.
1) Open SharePoint Designer > Right Click on Workflows and Select Properties.
2) In the Document Library Properties Windows, Select the Security Tab.
3) Select the "Manage permission using the browser" link
4) You'll need to adjust the permission for the appropriate SharePoint Users/Groups or Domain Users/Groups, depending on what you're using.
I've seen this happen to a couple of sites, and mostly appears to be caused very specific and custom permissions applied, which breaks the inheritance, and then the workflows are created by Site Admins or even Farm Admins.