You Do Need power plug adapter while traveling from Falkland Islands to Costa Rica.

Here is Why You Need An Adapter

The outlet and plug type used in Costa Rica are A and B and in Falkland Islands is G. This is how they look like.

Falkland Islands

In Falkland Islands, outlets of type G are in use.

Type G

Costa Rica

In Costa Rica, outlets of type A and B are in use.

Type A

Type B