Everyone lately seems to be looking for ways to cut costs on the trip of a lifetime. For me, it can be difficult to give good advice on how to do this, as to slash costs usually translates into a reduction of service quality or hotel quality that normally greatly reduces the value of the trip as well. I would say there are some countries (such as Guatemala or Peru) where you definitely do not want to skimp on guide quality or services, hotel quality, or transportation quality, as the end result will likely leave you wishing you had not visited the country in the first place!
There is however one destination where I would say it can be done, and done with relative ease and little noticeable lack in experience at all, and that would be Costa Rica. The tourism industry in Costa Rica is so well developed that you can travel to almost any region in the country and find someone who speaks very good english and knows the names of flora and flauna in English well enough to tell you all about the local wildlife in the area as any top knotch travel guide would do. While you may find it inconvenient to have to adjust to the various personalities of guides that you will encounter on the way, you will find that your overall experience will still be the trip of a lifetime!
I have put together though a spin off our most popular guided tour - Adventure Pacifica, that offers the "unguided" experience in Costa Rica. I have included locally guided excursions here and there along with free time in each area and a mix of pooled and private transfers to be able to offer a very affordable option that doesn't skimp on the experience! Take a look at it here: http://www.adventure-life.com/costa_rica/costa_rica_tours/tour/AP9-E.php5