Also, should have mentioned....we are flying out of SJ.

I would say either Savegre or Sarapiqui areas, depending if you want (a) a different climate or (b) monkeys. You'll see plenty of monkeys at Manuel Antonio, but both Savegre and Sarapiqui are known birding destinations that aren't as touristy as somewhere like Manuel Antonio or Monteverde.

Savegre is a highland setting so you can see birds like the Quetzal, etc plus mountain terrain, waterfalls, etc. Sarapiqui is a classic rainforest setting, so there'll be more wildlife and birds, with fairly flat setting and also more humid.

If you're looking for non-touristy, I would rule out Monteverde and Arenal as alternatives--the area around Arenal is especially touristy unless you stay way on the other side of the volcano at a place like Lost Iguana or the Arenal Observatory Lodge.

If you are staying in the Sarapiqui area and have your own car, you can drive to the operations centers for the Pacuare rafting companies, and you're guaranteed to see waterfalls on the Pacuare--you raft underneath the biggest one.

Personally I would still go to Arenal but stay somewhere like the Lost Iguana that's on the edge of town; that way you get all the activities that you're interested in, but still have that escape from it all jungly feeling. Hike La Fortuna waterfall, do the Penas Blancas river float or Cano Negro tour, kayak at Lake Arenal, and white water raft with Rios Tropicales. You can also hike at the Hanging Bridges and visit the natural hot springs like Eco Termales - they limit the number of people who enter so it doesn't get crowded.

Are you ruling out traveling via plane? The Osa is pretty easy to get to if you take a Sansa or Nature Air flight, and prices are pretty reasonable.

If I were doing the Osa, I would just skip Manuel Antonio though--nothing at Manuel Antonio you can't see at Cabo Matapalo, except tour buses and timeshares.

Thanks for all the suggestions. I'm leaning towards Arenal now. I'm not ruling out traveling by plane. Does anyone know how long it takes to drive from Quepos to Arenal? Is Monteverde worth a stop? We will pass by on our way to Arenal.

You won't pass by Monteverde on the way to anywhere--the map can be deceptive. I would skip and save Montverde for another trip.