Ugh...Please talk me out of Manuel Antonio...

You have to check out Drake Bay on the Osa Peninsula. It's way better, amazing hikes, pretty beaches. Lots of wildlife and very few people. It takes a while to get there but it's worth it. Especially if you want to spend 5+ days in one spot

Ugh...Please talk me out of Manuel Antonio...

Easy, don't do it, you'll hate yourself and your friends/family will hold it against you forever. Hope that helps.
I don't recall any good snorkeling in the area anyway, just a lot of people and an overrated beach and forest.

With 7 days go to the Caribe, Cahuita or Puerto Viejo or a nice a beach bungalow south to Manzanillo, all 3 have what your looking for. They are not that spread out, it's a 1/2 hour between Cahuita and PV and easy fun bike ride from PV to Manzanillo, really depends on what type of town/location you want.

Getting in at 8pm I'd just get a place in Alajuela for the night, very nice walking town 10mins. from the airport.
Set up a private shuttle for the next morning to get you to one of the above, it's a killer area.
Might consider rafting the Pacuare River on your last full day, it's a gas, they'll drop you off in Alajuela at the end of the trip.

Sorry for repeating a lot of what #3 already said... I wrote this before I saw his post.

I loved the Caribbean coast. Cahuita, Puerto Viejo and the beaches south of PV. That may sound like it is spread out but from Cahuita to Puerto Viejo by bus is only 30 minutes. And from PV to Manzanillo is also 30 minutes. Also, south of PV you can rent a bike and then just go from beach to beach. I would spend the first night in Alajuela (the town closest to the airport). The next morning take a bus from San Jose to Cahuita (for example at 8 am) and you will be there by noon. Spend two nights there. The Cahuita National Park is amazing: rainforest, beautiful beaches (some good for swimming) and lots of wildlife. Good hiking trail (almost 10 km return). Snorkeling only with a guide. Then choose a beach near PV or south of PV. We stayed in Manzanillo, a small village with a wildlife refuge. Great for hiking but better with a guide if you go far. We also walked to Punta Uva, nice beach. Lots of wildlife in that area. Snorkeling is supposed to be good in Punta Uva (the ocean was too rough in March). CR doesn't have great snorkeling so don't expect too much. As for the weather... I believe end of May/early June is not when it rains the most but there is a good chance it will rain. Usually late afternoon showers or rain at night. In March we had one day with showers and one day of rain. We still went hiking though and enjoyed the chorus of frogs.

If you really only want one spot you could visit the Cahuita NP as a day trip from the Puerto Viejo area.

http://www.puertoviejosatellite.com/

To get to Cahuita or Puerto Viejo from San Jose or to get back to San Jose from Cahuita or Puerto Viejo consider the rafting trip on the Rio Pacuare (the tour company picks you up at one end, takes you rafting and drops you off at the other end).

It's always been a dream of mine to make it to the Osa Peninsula... but I think the logistics of getting there and back eat up too much time unfortunately. Especially since the day our flight leaves it's at 7AM. It looks like getting there from SJO can be a full day or even 1 1/2 day event. I just wish I had more time.

Manual Antonio is a nice area and nice park, but its developed, and touristy. The park is small and all trails can be hiked in 2 hours. The beach is small and the majority of lodges are above the park and beach. Its a nice place to getaway from the capital for locals with family or a fun weekend at the beach, lodging at all budget levels. Its very popular, and has a lot of tourist...

But when it comes to nature/wildlife, and bio diversity, there are dozen better places to visit. MA is for lazy weekend tourist, or package tourist etc, its really not a place you should go unless you have very little time and want nature and beach, close to San Jose...

Otherwise, the key parks to visit, are Tortuguero, Cano Negro, Tenerio, Osa-Corcovado, La Amistad. For great beaches, hit the caribe side, or the many nice surf towns on the Pacific side...

The most overrated parks in the country are Monteverde & Manual Antonio, best avoided IMO.

Thanks guys! It looks like the PV Cahuita looks like it may be the way to go...the only snorkling I was thinking of doing was taking that trip out to Cano Island from Quepos for the day. My fiance has never seen really really clear water like that. So I take it the Caribbean side has equally good spots too then? Also, I like the idea of renting a bicycle and exploring.

I would not count on really clear water, its going to be rainy season in 2 weeks and sediment can make water not so clear, the pacific is not known for blue, more green, as the sand is brown, not white. The caribe side the same is lighter, but not white, more light brown....

Cano Negro is in the open ocean, 15-20ft to bottom, so snorkeling there should be early morning before the waves and swells build, but its nothing special. I would go to Playa Bellena near Uvita at low tide, long before Cano negro.

ON caribe side, there are areas in Cahuita NP to snorkel, but its better in Playa Chequita and Punta Uva, as the beach area is protected more from the wind. Its is the wind,that creates the waves...

I would not put CR on a shirt list for scuba or snorkel, its all about nature, wildlife and parks. You want to snorkel on a reef, which CR does not have one, so you should head to Caymans, Aruba, Bahamas, where the sand is light, and the reflection makes the water much clearer...

If you land at 8, you are not going anywhere, by the time you clear immigration its now 9pm. It gets dark at 6pm. You don't travel at night in CR, period. Shuttles and buses run in mornings always, and some early afternoon...but they like to get done by 5pm...