This is our first trip to Costa Rica and I'm hoping for one of the CR guru's on this post to let me know if our plans seem realistic for first timers.

arrival in San Jose - April 18th
hotel - Hotel Le Bergerac
day 1
- Pacuare River rafting
- drive to La Fortuna
- hotel - Montafia de Fuego
day 2
- Lost Canyon Adventures (Desafio Adventures)
- explore volcano
day 3
- horseback ride, etc... (Desafio Adventures) to Monteverde
- night tour of Monteverde cloud
forest
hotel Fonda Vela
day 4
explore cloud forest at Selvatura
day 5
travel to Manuel Antonio
day 6
explore Manuel Antonio - Mangrove Tour
hotel - La Posada
day 7
travel to San Jose
explore city a bit
hotel - Le Bergerac

day 8
return home

For me personally, that's way too much moving around and not enough time in any one spot. You're going to spend so much time getting from place to place.

Too many locations for too little time. Pick two of three for: Monteverde, Arenal, Manuel Antonio

I know it's hard to narrow down choices when you feel there's so much to see. However, you might be happier choosing 2 places with the amount of time you have. Keep in mind you're going to be eating up quite a bit in travel time. If you really want quick highlights though, only you know your personal travel style. There is also a Pacuare rafting transfer from San Jose to Arenal you might look into to eliminate driving to Arenal afterwards. You could easily add 1-2 more nights to both Arenal and MA and still have plenty to do. In Arenal the Cano Negro tour is great and you don't want to miss Eco-Thermales hot springs. Finca Valmy is a nice horseback ride in MA.

What are your thoughts about renting a car verses taking Interbus? Are the roads fairly well marked?

Yes, you should probably eliminate one stop so you can enjoy the places you do go to. Le Bergerac is perfect for a kick off hotel to the Pacuare River trip. It's the last hotel they hit before taking off for the river trip. (You'll love the Pacuare.) For the last night, though, the Bergerac is way out of the way. Somewhere like Vista del Valle or Finca Rosa Blanca is a laid back, relaxing place to end your trip before heading to the airport.

I agree, too much moving around. Transferring around CR is not as quick as it may look on a map. I would give more time to Arenal imho.

Driving is a personal decision, some love it, some hate it. A place like MA is quite easy to get around sans car while Arenal & Monteverde are more spread out and would leave you relying on rental cars.

Shillmac recently stayed at Le Bergerac and I don't think she was very taken with it, maybe she will chime in here.

I'm not sure where it is on the pick up list but I really liked Don Carlos for in town. Orchideas Inn for near airport. I've used Interbus several times and always worked great.