Dsus2/A ==> A, D, E
Dm/A ==> A, D, F
Cadd9 ==> C, E, G, D
Cadd11 ==> C, E, G, F
G7sus4/C ==> C, G, D, F
Cadd11 ==> C, E, G, F
Dmadd11/C ==> C, D, F, A, G
G5/C ==> C, G, D


There are a plethora of scales and modes to choose from, but knowing that the one you pick must contain A, C, D, E, F, G, like the chords do, really helps. The thing that the note analyzation does best is to tell you that you have the choice of playing either Bb or B, yielding two groups of notes -- A, Bb, C, D, E, F, G and A, B, C, D, E, F, G.

From the looks of the progression, it seems like the tonal center is a type of D minor. With the group of notes above, your choices are reduced to two scales - D Dorian and D Aeolian. Using Aeolian, with the Bb sounds more Spanish, whereas the Dorian sounds more Jazzy (BUT, you have to be careful, because the B can sound funny if you're not used correctly).

The above was written without actually playing the chords, so if the advice sucks, sorry! Haha, I think it should work, though. Care to record the backing and post a link to it? That way, I could try some stuff out over it and give a more definite answer.