Consider public or semi-public transportation for negotiating much of Costa Rica. No question: distances are vast, and your own wheels do offer you the greatest convenience. It’s surprisingly easy, though, to take shuttle transport, for instance, for trips around the Northern Plains. You could base yourself in Arenal or Monteverde and use occasional taxis to get around once you arrive. Many tour operators in both places are happy to pick you up at your hotel too.
Asked in the Forums: “If you LOVED Costa Rica…where else did you love the same?”