You Do Need power plug adapter while traveling from Ireland (Eire) to Puerto Rico.

Here is Why You Need An Adapter

The outlet and plug type used in Puerto Rico are A and B and in Ireland (Eire) is G. This is how they look like.

Ireland (Eire)

In Ireland (Eire), outlets of type G are in use.

Type G

Puerto Rico

In Puerto Rico, outlets of type A and B are in use.

Type A

Type B