How soon may I apply for a tourist L type, US citizen, for a 15 day tour beginning in March 2017?

My husband and I are taking a tour to China for the last week in March until the second week in April 2017. We'll shortly have our airline ticket confirmations but the documents from Viking Cruises won't be available for several months. How soon may we apply for our visas? May I represent both my husband and me to apply for and pick up the documents?