Who knows whether the decline to state (DTS) voters who requested a Republican ballot voted for Simon or for one of the other Republicans. More of the DTS voters probably chose Republican ballots than democrat ballots, because the Republican gubernatorial candidate selection was more interesting, but they might not have been motivated to request partisan ballots at all, and many might not have even known about the new law (even though it was printed prominently on the voter guide and sample ballots).
Supposedly, these DTS voters are all moderate, and they were all going to vote for the "moderate" Riordan, who was supposedly a viable candidate according to the media. Riordan lost by such a huge margin to Simon, so this group probably had little influence. I hope they are more conservative than the media think.
I don't recall any news reports of exit polls categorized by party affiliation. (Then again, I don't recall any exit polls last March....) The Statement of Vote issued by the Secretary of State did not have information about how many DTS voters requested partisan ballots.