Just returned from Costa Rica two days ago, it was great! I recommend the Marriott right outside the airport for your arrival and departure days. They have a free shuttle, it is a great hotel in the middle of a plantation, and it is only about 5 minutes from the airport. I also disagree with the no rental car assertion, we drove around a large part of the country with no problems. True there are places like the Nicoya Penninsula where most of the roads are dirt and in poor condition, so I would recommend a 4 wheel drive. None of the roads are impassible, however, and road signs were well marked everywhere. Just be prepared to go no faster then 40kph for the majority of your trip and you will be OK. Its not like an interstate in the U.S., but then if you wanted that you'd just stay in the U.S. right?