Will be spending one night precruise in San Jose Costa Rica. Need I convert my US dollars to local currency?

U.S. dollars have been accepted everywhere that we've gone.

Depends on how much you care about the exchange rate. And am not sure what you mean by "convert", I always use ATMs, but my bank charges no fees.

U.S. dollars and credit cards were accepted at every place I visited while spending three days in San Jose CR last year. The only exception was mass transit, which I presume you won't be using.

No matter where you travel around the world, credit cards (pretty much) always give you the best exchange rate -- just be certain to insist that you get the price in local currency. The second best rate is at ATMs, which are pretty common in San Jose.