As much as I understand your desire to have chickens, it is far better to be legal. If (when?) you are found out, you will be required to get rid of them, may have to pay a daily fine until you do, and there may be other penalties as well. In the meantime, you will have to be constantly on guard and hoping no one notices them and reports you or complains about them. In the event a neighbor's dog gets in and kills some or all of them, you will have no recourse because you shouldn't have had them in the first place.
I am lucky I am allowed chickens in city limits where I live BUT - I didn't get them until I found out it was legal to have them. And, when my neighbor's dog DID get in and kill them, I was able to call animal control and the neighbor was fined for not keeping his dogs controlled. Even hens can be loud when singing the egg song. Someone reported me for having a "rooster" on account of my hens egg songs! AC came out, looked at my set up, confirmed I have no rooster and we had a good laugh about it. That would not have been the case if I was keeping them illegally.