When it comes to deployment, each Droplet that you deploy will be provided with a unique IP. While they may be from the same or a very similar block, they will be unique as it's not possible for two or more Droplets to share the same IP.
So, for example, if you deploy three Droplets to NYC3, all three will have unique IP addresses.
That being said, there are instances where you'll deploy a new Droplet, destroy it, deploy another and the newest Droplet will have the same IP as the previous. This isn't something you can change though as, in most cases, IP's are provided at random -- in others, you may receive an IP that was previously assigned but not currently in use.