We have been in Samara at the end of June for the last 2 years, it was a great time to be there - afternoon rains on many days but not all, the wildlife is out in force that time of year.
The roads right around Samara (and from the Airport to Samara) are pretty good. We went for a few weeks so we took a transfer to/from the Airport and used Taxis or rented a car for the day for day trips (but if you only go for a week - you may as well rent a car at the airport since the transfers to town from Liberia is $100).
There is a lot to do around Samara, the only day trip I might make would be Nosara. Take a look at the middle of the following webpage for lots of details on what there is to do, restaurants, Nosara daytrip suggestions: