I spent three nights there, which felt like a comfortable length of time--we visited the petroglyphs, hiked up Concepcion, and hung out on the beach some. Be aware that the ferries can be canceled/delayed due to weather conditions, and have some flexibility in your schedule. We had planned to arrive mid-afternoon but ended up landing in Moyogalpa well after sunset, so it was good we didn't have anything planned for our first day besides settling into our hotel.