The hotel will offer various tours. The nearby beaches are pretty, but there's no waves and good snorkeling is within just a few areas. I think the trips from there to Arenal will be a very long day without enough time in Arenal/Fortuna. Instead you can go to Rincon de la Vieja (volcano and park), sunset catamaran sailing/snorkeling tours, maybe a canopy tour (I haven't been there).

Once you get away from the hotels at Papagayo, you will be in a different world-more like the "real Costa Rica". If you have a car, there are nice beaches to the south. Playa Coco and Playa Hermosa are popular with ex-pats. They have decent beaches, a bit crowded sometimes, plenty of a night-time scene, by CR standards. Lame compared to Cancun and similar.

Some of CR's best snorkeling is at Playa Ocotal, and you can stay there on the beach at Los Alamendros. Playa Conchal is pretty, and with decent snorkeling.

Area roads are good enough and the signage is usually good if you have a good map (the one with the Toucan on the front, available at Amazon).

Our favorite beach town in CR is Samara, about 2 hours south of Papagayo. Lots of info online. Just ask me if you want specifics.