It'll be just the same as hiring a bike from a bike rental on holiday.
They will look at you and suggest a bike for you to ride.
Perfect size for me is 55cm. My Spesh is a 54.
Last time in California, I hired a Giant which was 53.5cm.
Felt fantastic and I rode from San Francisco to San Jose rtn ( 100 miles ) without any problems.
Go for the smaller before the larger.
PS
Evans aren't going to prat about changing stems for a one day hire. If its 10 - 15mm away from theory, you will adapt your riding style to compensate.