HI Carey,
The difficulty obviously is that you can't run a report that includes both Projects and Tasks at the same time.
So, an approach could be to create a Task report and filter it based on a specific custom form being attached to the tasks. If your users choose to convert the issue to a Task they they would have to choose to add the custom form as part of the process (the risk being that they forget to). If your users choose to convert the issue to a Project, then they would need to be told to attach a template, which includes at least 1 task with the same custom form attached. That way, you should be able to report on the number of tasks with the custom form (field name is category.name) attached which were created (Entry Date) during a given time frame.
Cheers, David