For years I swore off Revere Beach, thinking it a litter-covered pit of despair covered with the likes of the Jersey Shore cast. Then I actually went there.
While you may run into a few characters, I found it to be clean and actually quite beautiful! Great views, decent water, acceptable facilities. It's accessible from the blue line, which is great! This week is the giant sand castle competition, so hopefully if you go, you get to see them (before the storm!).
For more of an adventure, you can get a bus to Southie (I can't remember the beach name but it's near Castle island). You can also get a bus to Crane Beach in Ipswich.
Beth