My husband and I want to go to CR in mid-July for our anniversary. We would like to go to fly in and out of San Jose and see:

Arenal/La Fortuna
Guanacaste
Tortuguero
Manuel Antonio
Monteverde

Is this too ambitious? How many days in each and what activities in each are "must" do without repeating in others? How would you recommend getting around (driver or rent a car)?

Thanks in advance!

Whether it's too ambitious or not depends on how much time you have. But, two weeks would be an absolute bare minimum in order to fit all of those in.

What would you recommend doing for ~8 days in CR?

Not to be glib, but do what you want to do. Without knowing what types of activities or experiences are your highest priority, there's no way to elevate some destinations over others.

You probably have time to do three of those destinations if you plan accordingly. I would also recommend looking at Sarapiqui as an option--wildlife and biodiversity there is as good or better than any of the places you've listed, and it's close to San Jose , Arenal, and Tortuguero.

San Jose to La Fortuna (2 days), then 3 hour drive west to the Guanacaste beaches (I like Flamingo and Conchal), OR go from La Fortuna right down to the beaches of the Osa (I like the area just south of Uvita; lots of beaches, parks, wildlife, waterfalls, scenery). You can even day trip to Corcovado park from the area (day hikes, mangrove boat tours, snorkeling trip to Cano Island; not the best snorkeling, but a fun trip).
Lots of lodging options.
We prefer to rent a small 4X4; never had any problems (other threads in this forum cover that).
My personal opinion is that Manual Antonio is crowded and touristy, and that you can see the same wildlife or better without the fuss down the road. Tortuguero is also a bit remote for a visit that includes the other places you mentioned.

I think we would definitely like to do 2-3 days in each arenal/fortuna and Monteverde. It's our third location we are having a hard time.

Throughout our trip we would like to: see lots of wildlife, white water raft, zip line, canopy tour, mangroves, small amt of beach time, volcano, hot springs, and perhaps a night time excursion (sunset, whales, turtles, etc for an idea).

We'd like to keep the traveling easy and not too difficult given the possibility of intense rain in July.

Any suggestions are appreciated.

I'd do Arenal, Monteverde, and Manuel Antonio; those are three areas that have a lot of infrastructure with lots of activities and numerous hotel and restaurant choices. Tons of tours you can do.

Tulemar Bungalows in Manuel Antonio is great. We love that they have their own beach and really easy access to wildlife - we saw howlers, capuchins, sloths, and aracaris on the property, and the views and service are fantastic, lots of nearby restaurants you can walk to as well. There's a nice mangrove tour called the Damas mangrove tour you can do through Manuel Antonio Expeditions. We also used them for a guided tour of the park and their guides are excellent and a lot of fun. We even go to one of the guide's homes for a meal.

You can do natural hot springs like Tabacon and Eco Termales in the La Fortuna/Arenal area and go rafting with Rios Tropicales. The Sky Trek ziplines there are fantastic, some of the longest, highest lines in the country. The volcano is here too, although not currently active.