SÃO ou SANTO = Saint ?

• O estado de São Paulo é responsável por mais de 33% do PIB do país.
• The state of São Paulo is responsible for more than 33% of the country’s GDP.

Use 'São' before names that start with a consonant, for example: 

São Luis, São Pedro, São João; Santo before masculine names and Santa before feminine names that start with a vowel; for example: Santo André, Santo Expedito, Santa Inês, Santa Isabel.

SÃO PAULO – Saint Paul

• A native or inhabitant of the state of São Paulo is called a Paulista.
• A native or inhabitant of the city of São Paulo is called a Paulistano.
• A player or supporter of the São Paulo Football Club is a São-paulino.    
•  fonte: Jack Scholes - http://www.teclasap.com.br