I just debarked this morning (Sunday) and was at PALO's last Thursday.
Although they prefer Ties/Jackets, it is definitely NOT a requirement. I nice Polo shirt is fine as long as it is with dress pants. I saw many individuals dresses with and without ties. I am one of those individuals who, quite simply, do not like to wear a tie as I find it constricting. Not to mention the heat and sweat.
Wear what makes you feel comfortable yet professional. To each his/her own. By the way..PALO food and experience is exceptional!