Ditto on the others' comments - definitely use a radio taxi (you pay at the airport and hand the receipt to the driver, so no cash exchanges hands in the taxi itself). Need to keep aware of surroundings- only 2 things I thought I'd add are:

1. Watch traffic late at night as drivers aren't required (or don't typically) stop for red lights between certain hours (something like 10 pm to 4 am) in case you're walking back later in the evening.

2. Expect peddlers to be relatively persistent along the beaches. I gave up being polite and learned that if they don't immediately leave you alone, only a strong no (or nao) works. They'll shine your sneakers if you let them.

Beautiful city. Flew into Santos Dumont the last time but view ruined by heavy fog/rain.