In addition, around 1,000 police will be staying on a cruise liner at Falmouth harbour and in camper vans parked at the RAF base in Newquay.
Social media images show caravans congesting the A30, leaving much of the road along the Devon-Cornwall border paralysed by traffic.
Secret Service agents will be staying in hired camper vans, as there is not enough accommodation for them.
All nearby hotels and bed & breakfasts are fully booked by holidaymakers enjoying the sunny weather, forcing Secret Service agents to pay thousands for the week.
The vehicles are expected to be driven to the Tregenna Hotel where President Biden will be staying for three days.