We went snorkeling in MA, and it was a dud for us. There can be sediment in the water that makes it hard to see anything very well; we did enjoy sailing. We just got a recommendation from our hotel for that.

We did Skytrek for ziplining too and it was great. You ride up the mountain on a cable car through the canopy, then come back down on a series of maybe 10 zip lines - platform to platform. There is a break in the middle at a little jungle cafe where you can get refreshments - they had complementary tea, juice, and water when we went, but I think you can buy additional items if you like.

For hanging bridges, they have a hanging bridge hike at Skytrek, but we went over to Mistico Hanging Bridges instead because we heard that it was better. We really enjoyed it - they have a bunch of hanging bridges over about a 2 mile walk. The walk was pretty easy and some of the hanging bridges were quite high and a bit scary to me, but I am kind of a chicken when it comes to that stuff. When we ziplined, I had too much adrenaline to be scared, plus the guides at Skytrek are really good. But just walking out on the hanging bridges made me nervous.

The Mistico Hanging Bridges are a nice hike. We've done it both with and without a guide. It's a loop trail so you don't need a guide, but with a guide you have a better shot at seeing some wildlife and learning about the area. We use Desafio for our guides, but sometimes they have guides available at the bridges if you want to reserve a guided tour. You can get nice volcano views if the weather is good. We only saw ants when we went on our own; with our guide we saw a toucan, a beautiful honeycreeper, and some howler monkeys at a distance. You never really know what you'll see. I'm not familiar the Spider Monkey tour. We've done canyoning and rappelling and enjoyed it. We used La Roca, but I believe they're no longer in business. Pure Trek is popular also.

I am enjoying this thread! A little over three weeks to go...

We are a family of 5 that stayed in many of these places.
 

We are a family of five that has followed advice from this forum, Volcanogirl has been offering advice here for many years! We have stayed in Tulemar and rented our villa directly with the owner, it was not VRBO we used but a similar service. It was two bedrooms and affordable. We have stayed at Si Como No as well but many years ago. Both were nice. We flew into SJO and headed straight to MA/Quepos area. Another time we came to SJO late in the day and stayed in SJO at El Grano del Oro. It was a beautiful hacienda that had been converted to a b&b/boutique hotel. In La Fortuna we stayed at Tabacon once but with 5 people we had more trouble. We stayed at Nayara and it was wonderful. We did the hanging bridges and the ziplining on the same day. I believe we went with Ecoglide? It was a fantastic experience. One time we took our remaining days and headed to Tamarindo (it was still a dirt road then!) and another time we went further north and stayed at a ranch. We flew out of Liberia that time.
I should one of our best experiences in CR was set up by our host in Tulemar. He arranged to have a friend bring his horses to our hotel and we took them to the beach. It was Sunday morning, no one was around and we rode them all morning in the surf. It was really special. You can search my trip report on this site if you would like all the details. What a great resource this page is! Thank you to all who have contributed over the years!

Hang, what a neat idea - that sounds like a wonderful experience. Lucky you!
We're also stayed at Grano de Oro and really liked it - great restaurant there.

I would definitely recommend Monteverde! It was my favorite. The cloud forest is truly surreal. Weather is gorgeous up there, food is fantastic. A little more expensive than La Fortuna area but in my opinion a must visit when in CR!

That's interesting that you found Monteverde more expensive than La Fortuna; that wasn't the case for us. Monteverde is pretty rustic by comparison. We didn't have good weather there, lots of pouring rain, and it was quite chilly at night; we had to wear sweatshirts and fleece jackets, and our hotel had their fireplace going. Still really enjoyed it though. Great place to try to see quetzals.