yea, thats what modes are for... this is touchy topic for me to discuss (check out the thread call-"shouldnt work but does")....A, B, C, D, E, F, and G are all the notes in the key of A minor, and that is because Am is the relative minor to C major. You can play those notes anywhere on the fret board...however A blues and A minor are two different things:
A minor-
E:-5-7-8-(A, B, C)
B:-5-6-8-(E, F, G)
G:-4-5-7-(B, C, D)
D:-5-7---(G, A)
A:-5-7-8-(D, E, F)
E:-5-7-8-(A, B, C)
A blues-
E:-5-8---(A, C)
B:-5-8---(E, G)
G:-5-7-8-(C, D, D#)
D:-5-7---(G, A)
A:-5-6-7-(D, D#, E)
E:-5-8---(A, C)
what ever scale you are using, you can play the notes in that scale anywhere on the fret board. I would suggest that you check out Afro's lesson on modes...hope ive helped...