Are the Jurassic Park islands (Isla Nublar and the Las Cinco Muertes) real?
No. The islands seen in the movies are not real; however, the Azores island chain is real, but it is believed from the continuity perspective that the island they wanted to use was also fake. Costa Rica definently doesn’t have an Isla Nublar and Las Cinco Muertes chain, another point to make is actually that the islands use improper Spanish and Costa Rica is a Spanish speaking country. Plus if there were, we probably would’ve had a San Diego Incident of our own and it’d be all over the news. It’s why the JP series is Science-Fiction at it’s finest.