To my knowledge, only start at L'Enfant. But call to see if possible to jump start anywhere. L'Enfant is the beginning and end, before they began again, over and over. Who knows, you may can jump on anywhere if you have your receipt downloaded on your phone to show you paid for the day.
You will need to call their main number and ask. When we went several weeks ago you had to check in and start at L'Enfant. During the busy summer season they may be more flexible.
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