Some people say NEVER block ribbing or cables, but IMO you can. You want your knitting to look finished all the time, not only when it doesn't include cables/ribbing. I might try it on the last few inches just in case I weren't happy with it and needed to undo a bit and redo... or I might do a spray block instead of a total wet block... or I might just wet block, depending on my mood. Do take a few minutes to mold the cables, which is kind of prodding/plucking them in to the shape you want.
The only caveat I'd have actually, is don't stretch them out too much while wet, they might get misshapen that way.