I upgraded to 5.2 and am looking for the "Find Declaration" feature -- the context menu doesn't show this in my project. Is there something I need to do to enable that feature?

I'm not sure what kind of declarations you are looking for. If it's a class of function or something written in php, there are two ways to follow:
-open file where the object of interest is used, right click on it and select Find Declaration
-open View-Tabs->Code Explorer and enter what you need in the Search input