Policies can become effective as early as the next day after your purchase. You can buy the policy on 11th for it to be effective on the 12th, or 15th for it to be effective on the 16th. It is better to buy the plan once you are sure of their dates of travel. You can even buy the plans after they arrive. However, it’s important to note that a plan will only cover any new medical situation that starts after the policy goes into effect.
Insurance rates are regulated by law. You can't find the same insurance plan for a lower price anywhere else