I am flying for a part 91 op. I'll be leaving soon and headed to the Regionals. I fly with another pilot who thinks he will never be able to do the same. Here is his problem and then my question.

He lived in Puerto Rico 3 years ago working as a bartender while building his hours. He was cited for DUI and involved in a minor auto accident. He didn't blow because he was afraid of the local govt and police. He submitted his written explanation to the FAA within the 60 days. Because he didn't blow there have been ramifications from the FAA. He has a "Limitation" on his medical. "Not valid for any other class after 6 months". Fortunately for him the result of his court case has been dismissed and expunged. Also, because it was in Puerto Rico it is not on his national driving record. I ran his pilot cert through OKC and he has no violations or accidents.
Here is my question; if he applies to a regional will he have to disclose this information? Will a regional even consider hiring him?

Will he be stuck forever in Part 91 and maybe 135? He's a good guy and a good pilot. Thank you for any info.