You will absolutely love the Renaissance. It is located in the heart of the action and the entertainment/restaurants/shopping is great. They have a really great happy hour up on the pool deck, and the Let's Go Latin Show is worth seeing one night.
As for transportation, the taxi's are great if you are looking to head over to the high rises. My husband and I did choose to rent a car for 2 days just to tour the island, which was a great choice. It was not expensive at all.
There are so many great restuarants to try! In fact, LG Smith's (at the Renaissance) is really good. We have been there on both trips. Pretty much where ever you eat is really good and top notch. The conceirge has really good suggestions, and definately take advantage of their services. Also, make sure you check out the Flying Fishbone one night!
You will have a fantstic and amazing vacation. I can assure you, you will be back!