You Do Need power plug adapter while traveling from Puerto Rico to Cuba.

Here is Why You Need An Adapter

The outlet and plug type used in Cuba are A, B, C and L and in Puerto Rico are A and B. This is how they look like.

Puerto Rico

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

Type A

Type B

Cuba

In Cuba, outlets of type A, B, C and L are in use.

Type A

Type B

Type C

Type L