I spent three weeks in July with my wife and kids. You'll get some rain, but it shouldn't detract from your stay. Some rain was a welcomed cool-down. It rained mostly in the afternoons.

If you are set on the three destinations you mention and are flying into and out of Liberia, for sure don't bother with Manuel Antonio. It will make too much travelling.

However if you are flying in and out of SJO perhaps it is Tamarindo that you could reconsider.

Like the other 2 posters, I really like July and most of the Green Season for visiting Costa Rica.

raquel.

Ditto what Raquel said. Although I am partial to our area, you can do most of what you want to do up in that northern zone and not waste a day or two driving down our way since you already have other stops planned. If you change your mind, we'd love you to spend time in MA, our economy needs you and it is beautiful and more green rainforest here! Enjoy!

I just don't want to miss anything. Are the sites and beaches quite similar?

Miss anything, you are not even scratching the surface. The best parks, eco systems and bio diversity, are not the areas you are even planning..

Tortuguero Canals, Osa-Corcovado, Selva Verde, Cano Negro are all more nature and wildlife than above.

Beaches, the best are the smaller surf towns on long and desolate stretches of beaches, like Playa Mal Pais, Nosara/Samara, or even Tamarindo/Grande, and on the caribe side, Playa Cocles/Chequita and Punta Uva...