i wonder if there is a place to look up which natioanl parks would have accomadations beyond camping. some times the towns near the parks where there are hotels are far from the park, and the parks not accessible by bus. which is my current mode of transport.
I was just there (only the southwest corner of the country) and also only using buses to get around and I was surprised by how the local buses actually reached the smaller more remote places. Many lodgings also offer to pick up from a bus station or at least give you explicit instructions on how to get to them from the nearest public transport with the rest being on foot or taxi (though be sure to ask the hotel/cabin owners the rough price to pay so you don't cheated, and try to get to your destination during the day.)
I stayed in Granada but took public buses to the Volcan Masaya and the white villages dotting Lago Apoyo where there were also alot of cabins/small hotels. From there you can take a tuk tuk to your final spot. Here's a place I spied (but didn't stay at: http://vianica.com/hotels/254/san-simian) Vianica in general is a pretty informative site.
On Isla de Ometepe, it was easy to get around from lodgings as their is only really a ring road all around the base of the two volcanoes and you just have to walk up to the parks on perhaps a few kilometres of road the split from the main ring road, but they are accessible almost 8 years ago