I was only at Ocotal for 1 weekend, so we didn't get out to eat. The nearest town is Liberia, and it's kind of a hike to get there. The food at the resort is just OK, but there's a restaurant on the beach that used to be owned by the resort, and still has an agreement that allows you to charge meals to your room. It's got atmosphere and decent food.
As far as car rental goes, if you're only going to be there for a weekend, don't bother. However, if you're going to be there for a week or so, you might want to rent a car to see some of the other tourist sites (Arenal volcano, Tabacon resort, white water rafting, rain forest tours, etc.). It will help if you speak spanish, and even at that, you'll be taking a real adventure. I wouldn't keep the car for the entire week, as car rentals tend to be quite expensive (I believe it has to do with the import taxes they put on new vehicles - it effectively doubles the price of the car). Alternatively, I expect the resort can set you up with a tour group that will take you to these places.
Hope that helps.