Can spanish speakers understand portuguese

This depends.

Explanation: Portuguese is simular to Spanish. People from Spain will most likely be able to understand some Portuguese from Portugal and other states in Brazil (not Rio De Janeiro because the accent is too different). Most Spainish speakers around the world will understand some Portuguese although it is easier for Portuguese speakers to understand Spanish.

(Portuguese is spoken in Brazil, Portugal, Mozambique, Angola, and other countries and border brazil like French Guiana)

The Rio accent is called Carioca. With this accent most "r"s sound like "h", "d" sounds like "g" and most "t" sound like "chi". Carro sounds like cahho but caro sounds like caro. (carro means car and caro means expensive.)