Actually, those were probably the best words you could have used. The two best defenses to a defamation action are truth (what I said was true) and opinion (can't be proved true or false). You words would seem to fall into the latter.
A couple of points. First, it does not matter that you used the word public. Second, published means communicated to a third party not the subject of the statement. A to C about B is publishing.
If you say "ABC Restaurant has been cited 15 times for having rat feces in the food" and its not true, then you have a probelm.
On the other side of the coin, if you say "ABC Restaurant is the absolute worst place in the universe to eat" there is nothing they can do to you. Its an opinion.
I would want to see the entire letter before rendering a final opinion, but I doubt they have a cause of action against you. They could still sue, but winning is a different matter and I don't think a reputable attorney would do it based on what you wrote.
I concur with Mr. Garner. Also, if the statement was prepared for use in the court cases, the contents would be privileged and its publication would not subject you to liability for defamation. (See Civil Code § 47.)