Applying as early as possible is a golden rule. How have your practice tests been? Or have you even started studying taking them yet? If you feel comfortable with you range of practice test scores by June, I would say go ahead and apply. You can apply to just one school if you want and add more after your app is verified and you get your scores back. As peak application season hits during July-August, verification can taken substantially longer than during the first few weeks in June when far fewer people are sending in their app. That way if you decide you want to wait a year, you can withdraw your app from the one school with the benefits of not losing a lot of money on primary/secondary fees of additional schools, not using up one of your application cycles on your top choice schools (i.e. having to be reapplicant to a school you withdrew your application from because you decided to wait a year), and also having a well drafted personal statement/ECs. Conversely, if you get your scores back and are happy with them, you can apply to more schools. Unfortunately for you, you won't know your scores until August, which is still kind of late for applications. So I would say it really comes down to how well you are doing on your practice tests and how ready you feel for the mcat.
Also, are you international? Typically the phrase "writing the mcat" are indicative of an international student.
