Want to book award ticket for a US flight PHL-PBI (West Palm Beach, FL). US has the award seats available but I really want to burn my soon-to-be-expiring UA miles. UA will sell me a codeshare ticket, but not an award ticket. Do I have any options?

Check FLL instead of PBI?

Make sure to call UA to be sure you are investigating partner (in this case, US) travel options.