Hi Andy,
If you are planning to go to Drake Bay and see Corcovado, you can easily spend 4 or 5 nights there. With the other couple nights you could consider staying near, but not in, San Jose and taking some tours from there. We really like a place called Hotel Buena Vista, which is in the hills outside Alajuela. It is still close to the airport but feels very secluded in the mountain. They offer day-trips like a coffee tour and a visit to Poas Volcano, plus have an airport shuttle, so not having a car would be fine.