I get the normal dialog box box when I choose Save As on a Safari page. How and where I want it saved.
This function is controlled by Finder, so I think step 1 would be to reset your Finder prefs.
Go to your Finder "Go" menu hold the option key and choose Library. Then go to Preferences folder and trash this file:
Then, restart, or log out and in again.
(You will have to reset a few finder prefs the way you like them.)