marni, are you using the Sculpty Maker converter made by 2k Suisei? It is made specifically for use with zBrush. I use it all the time and have never seen results like the map that you posted. I have seen that sort of grid effect form other converetrs - like the Object2Sculpt program.
2k has recently updated his converter - you can find it on the LL forums:
SL Forums
You can also download it from my Shiny Life site:
Shiny Life SculptyMaker Updated to v1.5 | Shiny Life