I have one of eight garden-style condo units located in a single building. All of the meters (with main breakers below) are located on an exterior wall. However, neither the meters or breakers are marked with unit numbers. Aside from testing them all, how would I identfy which meter/breaker goes with my unit?

You should have a main breaker in the panel in your unit. Turn it off and observe all of the meters for a period. The one that does not move is yours. Confirm that by turning off the main breaker at that meter. Turn the main breaker in your panel back on and turn on a light switch.

You can also contact your utility and give them the meter numbers. They can confirm which is yours.