It holds 4 people including the driver in the vehicle.
Notable owners in GTA Vice CityEdit
Ricardo Diaz: Owns a bulletproof and fireproof Admiral
Ken Rosenberg: Only appears in the first mission
Amy Sheckenhausen (Host of radio station K-CHAT): Although she never appears in the game, she is thought to own a Admiral.
The Admiral will mostly appear on the roads while they are being driven by the pedestrians. One other location is Starfish Island in front of the mansion closest to Vice City Mainland entrance to the island. You will need an air vehicle to access this.