We stay on the French side and often drive to the dutch side in the early evening for dinner, returning after dark and have never encountered a problem. We always have traveled through the south side of the island. Our rental car person recommended leaving the glove box open and don't even leave a bag of trash/beach towel ect. in the car to temp. We have left luggage in the trunk at the Maho beach parking lot while having lunch before our flight with no issue.
And I have been in the airport and witnessed a couple sobbing hysterically whose luggage was stolen from the car when they went to Maho pre-flight. It's the risk you take if you do that IMO.
I have had my car rifled through in Maho at night. Back when there was nightlife at Sunset and the place behind it. Came back and the trunk and doors were open, glove box open. This was 1995. Even back then we were taught to leave the car unlocked.
