Been a little while since AF1 visited Florida and according to news reports will be returning on Tuesday Sept 8th, landing at Palm Beach Int'l Airport a little after 2pm prior to a POTUS visit to the Jupiter Inlet Lighthouse and Museum about 3pm.
Try 260.9, 228.9, and 247.05 Search the UHF mil air band they may change depending who is providing tanker and fighters but the first on has been fairly consistent.