BOOKING ACCOMMODATION IN NICARAGUA

I am going on a month long trip to Nicaragua from 25th February 2013. I want to be very flexible with my trip. I hoped to just book accommodation as I go and to not plan a set itinerary. I thought we would start with Little Corn and I have just tried to book for the first 3 nights of our trip. Most of the places are booked already, 3 weeks in advance. This makes me concerned that I will need to book all of my accommodation in Nicaragua weeks in advance and cannot be as flexible as I want. Is this correct? Or is it just that Little Corn is so popular and with relatively few places to stay? Any help very much appreciated. Thank you