It was a van:
At about 6 a.m. Sept. 11, Longboat Key Fire Marshall Carroll Mooneyhan was at the front desk of the Colony Beach & Tennis Resort as Bush prepared for his morning jog. From that vantage point, Mooneyhan overheard a strange exchange between a Colony receptionist and security guard.
A van occupied by men of Middle Eastern descent had pulled up to the Colony stating they had a “poolside” interview with the president, Mooneyhan said. The self-proclaimed reporters then asked for a Secret Service agent by name. Guards from security relayed the request to the receptionist, who had not heard of either the agent or plans for an interview, Mooneyhan said.
...
Earlier, the FBI questioned a Longboat Key man who also had a strange run-in with a van occupied by men of Middle Eastern descent.
At 8:50 a.m. the man stood on the Sarasota bayfront waiting to watch the presidential motorcade pass. A dilapidated van passed him with two men of Middle Eastern descent “screaming out the windows, ‘Down with Bush’ and raising their fists in the air.”
http://www.longboatobserver.com/showarticle.asp?ai=1874Hopsicker says it was white (WtTL, p. 45), but he didn't talk to Mooneyhan, so how does he know?
I guess there are plenty of white vans with men of Middle Eastern descent in Florida, though.