It's an iffy proposition. Notes aren't deleted so much as the server is asked nicely to delete it, or maybe at least hide it, and if it makes it to the client, the client can decide if it wants to honor that request as well.

If someone has a chance to interact with your note in some way, and they use different relays than you do, your note will get copied to their relays and your request to delete it will never make it over to theirs (did that make sense?)