We spent four nights in Manuel Antonio at the end of our trip and I think we both could have just stayed there for our whole time. The place we stayed helped (Lunatica guest house) but the entire area is just amazing. The beach outside of the national park was as good as it gets with strong, warm waves and an incredible view. The national park was very cool even though we didn't have a guide... saw an awful/amazing spider and many monkeys.
We will definitely be back and for a much longer time!