We stayed at La Mansion Inn during the second weekend of March, and enjoyed it very much. It's a small hotel, but every room seems to have a great view of the ocean. If you head up to the pool and patio area, you'll see 360 degrees of spectacular views of the area.
A couple of downsides, for me at least: They don't have a buffet breakfast, instead you order off the menu, and it's all complementary. Also, if you have a rental car, the driveway and small parking area are very hard to maneuver. In fact, the whole Quepos/Manuel Antonio area seems to have a cramped feel.
Otherwise, the staff is very attentive and the rooms were very clean.