We found it VERY easy to navigate around, the roads are very well signed, and nothing is really all that far from anything else. I don't think I can ever bring myself to go without a rental car again. We do also use the bus transportation at times, but it's so much more convenient.
Make sure you remember to get the parking pass at your resort when you check in, and just this one tip about that - be VERY careful when driving around with the windows down. We almost lost ours a few times. Either stow it someplace else while in transit, or bring a small roll of scotch tape along to give it a little help staying in the windshield.