Last time I was at the Palafox Marina I asked. The guy said that they have a transient slip you are welcome to use. It's free of charge if you don't spend the night. But I'd call them to confirm and confirm that it's empty or that you can tie up elsewhere if it's not. Please post what you find out.
I called the pier today and spoke with the dock master. He says he would find me a spot as long as I called a little in advance (same day). He was a very nice guy and said if I were only there for a few hours for lunch or dinner, there'd be no problem or charge.