I am not familiar with the roads near the Four Seasons, but recently travelled all over the island. Unless, it’s a major highway, and there not many of these, most roads are twisty, exceptionally narrow, can be very hilly depending upon the region, rough, pot holes galore, many are dirt, and would be a nightmare to try and road bike on them.

Running and swimming should be fine. Lots of cool things to see if you have any free time, rain forest zip lining, Arenal Volcano, great local food, etc.

I've actually ridden right by there coming from the opposite direction and turning around at the Four Seasons as a halfway point. It's not the best place to rise but if all you want is to get some riding in it's certainly doable. Pavement is decent for the most part and there are some hills including some steep parts. There can be a fair bit of traffic and most cars are pretty good about cyclists there but the big tour buses are not always the best and you would definitely be seeing some of those.

I don't know where I'd drive to ride from there at this point if you want to try to find something better. I went and trained there in 2019 and it was pretty good and then went again this year and there are far more cars on the road than there used to be. I was told that everyone used to use public transportation but when that all got shut down for the pandemic everyone bought cars and they just decided to keep using them.

Bottom line, you can ride right from the hotel and be ok to get a ride in but I guess it depends on your comfort level with cars and how long a ride you are looking to do. Can't really help with running or swimming as I didn't do any near there but I would imagine there would be some decent options nearby since they used to have a 70.3 near there.

There is a FB group The Crew which is based in Costa Rica.. they are a group of triathletes and other distance endurance sports.. they might be able to give you some local insight.