Virtually any Jeep you'd rent almost anywhere is the cheaper 2WD version. True 4WD Jeeps cost a small fortune to rent because they know what people are going to try to do with them. I don't know of any national rental company that rents true 4WD Jeeps... Have to go with local boutique/specialty car rentals to get one.
Perhaps almost anywhere, but not in Dominica, at least not the last time I was there a few years ago. I've always rented a 4 wheel drive Japanese SUV for about the same amount as a regular car during the dozen or so trips I've made to that wonderful island with its very bad roads.. Never a Jeep because Jeeps are mechanically inferior to almost anything out there. Most renters wanted a 2 wheel drive automatic shift because they had never learned to drive in the full sense of the word. One of the last times I rented a 4 wheel drive SUV in Dominica they at first brought around a two wheel drive auto shift. I refused to go near the thing. The rental agent at the airport told me that Americans could not drive a stick shift, and besides, I was already in my 70s at the time. Eventually he had a 4 WD brought up and got into the passenger seat. "Let me see how you go", he said. I drove around for a few minutes until he was satisfied. He was gracious enough to apologize, and gave me q 10% discount for my trouble.