I just did some of these a few days ago. In the past, I have done it both before and after dyeing.
The last ones were printed in black only, so no big deal.
Usually (and I recommend) black and white so that designs are more likely to show in more possible dye color combinations.
When I have printed white, the subsequent dyeing didn't take to the plastisol(as already reported), but if there wasn't great coverage (which is, of course a little tricky to see on a white shirts) there was a hint of color peeking through.