February is a great time to visit Santa Teresa. The roads are usually in much better shape and the weather is full on sun!
1) Supervista bungalows are right on the beach. If you like the sound of the waves and to be within a stone's throw of the water, then this is the place to be.
The down side is that you are directly 'at' the beach and everyone walking by can see onto your deck and into your bungalow (especially at night), there is no shade and the bungalows can become ovens during the heat of the day. Quite honestly, I would find this very uncomfortable and would not be able to feel relaxed about this....but, that is my personal opinion. If you are looking at more private accommodations and not quite so public, perhaps you want to check out www.nicoyazoom.com and compare prices and locations and amenities at other places in the area.
2) Renting a car is a good idea. You can do this near the airport and drive down to Santa Teresa and experience the ferry system and see some of the country. It will take about 1.5 hrs. from the outskirts of San Jose to the ferry, another couple of hours dealing with getting onto the ferry and the trip across the gulf and then another 1.5-2 hours to Santa Teresa depending on how many stops you make along the way. Remember to do the drive during the daylight hours (roughtly 6AM to 6PM). If you are going to be exploring, you will need a 4x4. You can also fly to Tambor from SJO and rent a car when you get to Tambor or Santa Teresa (I recommend reserving the car before you get here because it is high season).
3) Some parts of the ocean in the area are good for swimming, many spots are good for surfing and boogie boards. You will have to ask for specifics when you get down here as the area and beaches are vast and there is a lot to choose from depending of you activity of choice and skill level.