Personally, I don't have any experience in this area.
It does seem like dementia is a growing concern in the country.
I would try contacting people here to look for more info: https://findahelpline.com/countries/cr/topics/dementia-alzheimers
a nursing home: https://nursinghomescostarica.com/ & https://verdeza.com/
Good luck and let me know if you have any other questions.