South American,
Whether you need to hurry up or not depends on your number. The lower it is, the sooner your interview will be, starting in October.
If you are applying for consular processing, you can mail them at any time. Then, depending on your number and when you sent in your application, your interview will be scheduled. For example, someone with a number EU00015000 sends their application in July. Someone else has a number EU00014999, and send their docs in September. It is logical to assume that if the numbers become current in the same month, then Person A will get his interview scheduled a couple of days sooner.
Now, if a person (A) with a very low number EU00000050 sends their application in September, while a person (B) sends their application in June. Person A will still get his interview sooner, because their number will be current long before Person's B. However, if person A waits until January to send his documents in, chances are the interview will be scheduled much much later....
If you are in the States, and will be doing AOS (adjustment of status), then you don't have to worry about sending the docs in until October. And even then you can only send them in when your number becomes current.