Here are the areas I know:
La Fortuna - mid-sized party town, near a bunch of mountains and volcanoes that you can do day trips to.
Tortuguero - National Park on the Caribbean Coast - pretty cool - definitely go if the turtles are laying eggs
Monte Verde - cloud forest, really cool temps - do the night walk and hikes and zip line if you’re into it.
San Jose - I loved the Barrio Escalante neighborhood. This might be your best food options in all of Costa Rica. Look into Finca Escalante hostel for a great central location and lots of other travelers to meet. Look for the restaurant with the big zebra.
Tamarindo - pretty fun beach town, not too douchey. Seek out the restaurant that’s famous for its pineapple pie. It’s incredible.
Jaco - super coked-up douchey beach from what I hear.
Drake Bay - probably my favorite place in CR. Super laid back vibe because it’s hard to get to - lots of stuff like scuba and day trips to 2 different national parks. You can drive but it’s easier to take a boat from Sierpe (you can leave your car). I could spend a week here easy. Look for Hostel or Hotel Margarita.
Dominical - laid back beach, lots of surfers, only spent a day there but it seemed nice
Quepos - best place for diving. Nice national park nearby - Manuel Antonio. We stayed in a hostel in the non-touristy regular part of town more inland and I loved feeling like I was local.
Baldi Hot Springs - upscale resort place with tons of different hot springs and some incredibly dangerous water slides. Good place to go to pamper yourself and the wife for a day.
Liberia - gritty town, not dangerous but not touristy