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

Here is Why You Need An Adapter

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

Costa Rica

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

Type A

Type B

Guyana

In Guyana, outlets of type A, B, D and G are in use.

Type A

Type B

Type D

Type G