We're similar in age, and have always enjoyed renting a small 4WD; roads are paved and fine, if winding in places, just about everywhere you will want to go. However, if you decide on Monteverde from Arenal, the ride is scenic, but bumpy, and you WILL want a 4WD.
You could go to Arenal for a few nights (and Monteverde), then drive to Dominical/Uvita for the wonderful beaches. You can visit the Osa from there (about an hour to Sierpe). Day trips to Corcavado NP leave from the little town of Sierpe, along with mangrove boat tours and snorkeling Cano Island. Then back to SJO (you could take route 2 through the mountains for a scenic way back).

A potentially more relaxing alternative is to take a shuttle such as Interbus to/from San Jose to Arenal, and then fly to Dominical and/or the Osa. Or you could hire private drivers.

Of course, this way you'd need to have enough to do wherever you're staying, or rely on local taxis, tours or buses.

Pros and cons to both options!

The Arenal area is our favorite. If you're up for a great zipline, check out Sky Trek. The Cano Negro tour and Penas Blancas river float are nice ways to see wildlife in that area. I think you're fine to drive to the Arenal area, but I personally would fly to the Osa. Be sure to check out the waterfall and the natural hot springs as well. The Hanging Bridges is a nice hike in the area.

Exciting! Enjoy your trip! My boyfriend and I went for the first time in 2011. We left with no plans, other than a reservation for a hostel in San Jose.

We got some great ideas from the folks (and owner) of the hostel and figured out the rest of our journey from there. We took a plane to Nosara for some surf & yoga, then rented a car, stopped overnight in Nicoya (found a bull-fight festival) on our way to Arenal (stayed at the Baldi there and did ziplining). We drove back to San Jose and then took a bus to Puerto Viejo. We absolutely fell in love with the relaxed reggae feel of the Caribbean coast and are headed there TOMORROW! Wooo! It's only a 5 hour bus ride and $9.

I hope you two have an amazing time! If you guys cook while you travel, you might find my latest blog about my International Mobile Kitchen interesting. http://adventurouspalate.blogspot.com/2012/10/the-mobile-kitchen.html

Pura Vida!

~Angela

Thanks everyone for your responses. Our budget allows us to spend somewhere in the neighborhood of $1500. total for places to stay. We appreciate good views close proximity to the beaches when we head south, comfortable beds, clean rooms, and good tasting food. We are not fancy people. Any recommendations are much appreciated!

hi Bucketlister

You should have no problem meeting yr budget. In Arenal, Silencio de Campo, Arenal Observatory Lodge, Arenal Manoa, and many more offer up great views.

As for beach hotels, your options are really broad, although what you need to do is narrow down you choice of beach(es). If you're really adventurous, you might want to take that car as far as Playa Zancudo (Los Cocos or Sol y Mar), you'd stop on the way in Manuel Antonio (perhaps Karahe or Verde Mar) and Dominical (Roca Verde or La Cusinga or Costa Paraiso or Villas Gaia. At Zancudo, tour around the Golfo Dulce w/ Zancudo Boat Tours. Although that does leave you with a long drive back, which you might also want to plan on breaking up and then timing might be getting tight....

The Lost Iguana is a great hotel in the Arenal area; they offer a lot of good specials/deals. Silencio del Campo always gets good reviews as well.