Well, I guess you knew that this was coming ... you need to learn the major scales. Of course, it is possible to play music without knowing them but you will know true freedom of musical expression if you take the time to learn them.

The good news is that we will be learning the scales only on the last three strings (G,B and E), and believe it or not we will learn ALL of the scales by memorizing just six of them (seven, if you consider C,D,E,F,G,A,B,C memorizing.)

So at the most you will have to remember three sharps and three flats.

The keys you will have to remember are:
C,D,E-flat,F,G,A and B-flat.

Not bad if you consider the alternative ... Memorizing all 23 scales