I am very proud of this cheats because I found all these cars by myself and not looking in any magazines or web-sites.

Miami:
1:) Go Cart: Head to the 'Coral Gables' at the end of the map. There should be a rectangular shaped road with a big building at the end of it there. Head towards the big building and you should eventually come to a crossroads. Turn right at the crossroads and just go straight and you will go through through a big gap in the wall ahead of you; keep on going until you see an entance to an underground passage way; like a sewer type place. Go through through here and once through the other side you should see a set of stairs to your left that lead you to a door on the wall in front of you, you should also see a closed gate in front of you. Go up the stairs and follow the walkway to that door (the door has a sign that says 'Gate Control' next to it); go through the door and kill the 'Timmy Vermicelli' behind the barrells, and then press the switch on the wall. Head back out the way you came in and the gate that was closed should now be opened. Head through it and you should come to another courtyard type place, turn left and follow the the route through. At the end of the route there should be a big hole in a fence in front of you, go through the hole and you shoud see a race track in front of you, turn left and find the start of the race track and in the 'pit area' there should be a little go-cart that you can drive. Once you get in the go-cart another go-cart will come along awho you will be able to race. Once you start to race around the track a timer should appear at the top of the screen to create a fun little mini game as well!

2:) Sports car: To my amazement, my Dad actually found this secret, and my dad dosen't play video games! On the bridge that has one of your safehouses along it, there should be a little road just before it (still on coming off the bridge) that has a dead end. Go down this road and there should be a garage at the end of it which should open automatically when you are in close proximity of the door. In the garage is a really fast sports car.

Nice:
1:) Forklift: Right at the south east end of Nice, there is a longish strip of grass land that, according to the map, has no roads on it. Go to that area and there will be a road on it. Follow the road until you reach a road coming off of it sloping upwards, head up that road and there should be a garage in the corner of a garden. Go up to the garage and the doors should open automatically when you are close enough. Inside there is a forklift that actually works! press the circle (or 'Burnout') button to make the fork go up and down. And Yes you can flip cars over with it!

2:) Bad Hand's Van (Hippie Van): Go to the place called 'Cagnes Sur Mer' at the North West of Nice. There should be a series of winding roads sloping upwards. Make your way up the hill until you reach the very top. You have to speed up the last hill that you go up as you have to jump over a wall that blocks cars from going any further, or you can just walk through the archway at the top. Once at the very top, look around until you find a garage. Once you have found the garage, go up to the door and it should open automatically, inside the garage is a Hippie VW type van that you will recognize as Bad Hand's Van if you have got to that mission in Undercover.

Note:Once you have driven a secret car or killed a 'Timmy Vermicelli' the game won't autosave your free ride data so REMEMBER TO SAVE TO YOUR PROFILE MANUALLY OR YOU WILL HAVE TO KILL ALL OF THE 'TIMMY VERMICELLIS' AGAIN! Also, if you save your data once you have driven a secret vehicle then you will be able to start Take a Ride mode with that vehicle and won't have to go around looking for it again!