Good job, OP, but I think your reply is just too wordy and one struggles with the beginning. You give a negative example 'most people...blah, blah, blah'. We all do this, trying to be meaningful and erudite, but the truth is the best reply is:
1. Re: my letter of (date) thank you for the reply and the consideration, and
2. You changed the signs about carrying and
4. That made me (and the state law) happy
5. Thanks for your quick and favorable response.
6. Who can I compliment you with
7. Yours truly.
You probably already sent it, so it's a moot point, but, if I can be so bold as to suggest, we all need to consider that public officials get tons of mail and look most favorably on:
1. Knowing what the heck you're referring to (i.e. 'my letter, when and why')
2. What they did
3. How that made you happy/satisfied and conformed to state law
4. Thanking them for their promptness
5. Giving a pat on the back.
6. Emphasis on you being polite and thoughtful
I've found a good closing is 'please let me know the email of your supervisor so I can compliment your attention to this important matter'.
Then I'd carry their reply with me so you can offer proof of intent in case you get stopped before everyone is briefed. Again, good job.