I would also recommend tracking down copies of Charles McNeil's chord system for tenor banjo (shows both actual and octave notation) - I think you can purchase a download a copy at Django books - and his one for plectrum banjo. The latter you can access for free as Banjo Hangout member, Joel Hooks, posted it here:
The MacNeil Chord System book is not only about chords, but a complete course about learning tenor or plectrum banjo. It is intimidating, but with a good teacher, it is probably the best lesson book. It will take a beginner 2-3 years of weekly lessons to learn. I know. Jim
I can't supply resources, but I can give some advice:
The only real way to learn is to read a lot of different songs. Pick up an unfamiliar tune and play it once and once only. Then go to another song, and another...
The idea of playing a piece once keeps your mind and muscles from memorizing that piece, and forces you to read the just the notes.
Mix the reading exercises into your regular practice routine and do it daily.
The perfect answer. You don't have to start with a whole piece such as the Bach. Pick four or eight bars each day and start with music that had a lot of step-wise motion and then look for music with more jumps. All of that is in the Bach Prelude but not in the order that I would use to improve my sight-reading skills. Familiar tunes can be helpful or a hindrance. Helpful in terms of playing the right notes, but often the wrong rhythms if you play it the way you think it goes and not exactly the way it is notated. Remember, there are only seven letter names in music. I have always told my students' if you can memorize a girl or guy's phone number that you like, which is a series of numbers in a random order, learning pitches on a stave is a walk-in the park. Rhythm can be done separately away from your instrument. Use a metronome and "sub-fivide and conquer" in your head and use a metronome. Accuracy is more important than speed. Both of these facets are basic tenants of sight-reading. You can practise them over and over separately and away from the instrument, but when you put them together, do exactly as Edward said above. That is where you put the two together and just read. For rhythm there is a great book by Hindemith but there are many resources for sight-reading. Probably way too many!
PS After fifty years of playing, and two music degrees and 40 plus years of teaching music I still find spelling the word rhythm is much more difficult than learning to read rhythms!!!!!