Story on crossing at Peñas Blancas
I just read a personal experience article about a person traveling from Liberia Costa Rica to, ultimately, San Juan del Sur. I have labeled it personal experience because it is just that. What I am saying is that it covers what one family experienced. It is not a good guide for how to do it but it might help you get the feel and possibly avoid some of the mistakes they made.
The article is on Gadling. It is not just my assertion that the article is not the right plan as it is titled How (not) to walk across the Costa Rica Nicaragua border. Those of you who have made this trip can probably find 10 things that could have been done better but the mistakes they made are certainly not out of line for a first time.