Legal or financial barriers to driving a rental car from El Salvador to Honduras?

Since I (apparently) can’t fly from SAL to Choluteca, I was planning to drive.  But then I had to think some more: Will I be required at the Honduran border or at the rental counter to show an international driving permit (IDP) or pay an extra fee for leaving the country with it?  Or buy/show insurance beyond what I normally get from Allianz?