I agree if you plan on going to El Yunque, I would avoid a compact but nothing too big as the roads are rather tight at spots.Agree with MickiSue that your credit card rewards would help extra cash back. I have been there a few years ago, and I rent from Charlie car rental (local operator). Okay experience but I have used United explorer card at that time for better coverage.
One thing to be aware of is to watch out for all those potholes there. Roads are not good in Puerto Rico at all.