Im not sure but i searched google and found a flyer about citizens reentering into the country and visitors saying pornography is prohibited. Plus you have to pay import taxes for stuff bought outside Costa Rica. Question is can you go to a store and pick up a dirty magazine or dvd? If you can then you should be able to import it from here, but you may have to pay 37% of the value to the tax man at the postal place or when he delivers it. Im not sure because i never had to pay a tariff up front.
I think Jacob has the system that you won't be able to buy if it not legal to sell or ship. You may ask the store or jacob himself.
https://www.fakku.net/contact
I can't read Castilian spanish so i can't translate the custom office site.
http://www.hacienda.go.cr/contenido/284-servicio-nacional-de-aduanas