Hi Bev,
I could have sworn we answered this question the other day but now it’s not showing up. Anyway, here are some ideas for hikes in Guanacaste. The area in general is pretty flat but there are a few good options:

• Diria National Park– Little known park near Santa Cruz and an easy day trip from Tamarindo/Flamingo area. We saw 2 different kinds of monkeys and lots of birds on our visit. Here’s a blog post we wrote with more info: https://www.twoweeksincostarica.com/diria-national-park-hiking-near-guanacastes-gold-coast/
• Palo Verde National Park– We haven’t been there yet, but this is a large park that is good for birding located off the Interamericana Highway. You access it through a ranger station near the town of Bagaces.
• Santa Rosa National Park– Another park located in very northwestern Costa Rica. It’s has tropical dry forest and abuts the ocean; there’s also a historic site from the battle involving William Walker and the filibusters.

If you ever get down to the Southern Zone, we’ve got lots more ideas for hiking there. Probably the best part of the country for hikes!