From The Main Menu, Select Options Then Cheat Codes (Case Sensitive)
To unlock the following vehicles, complete the following.
The best car to start your career with is the SRT4.
If you have midnight club 3 dub edition then save it on both memory cards(if you have 2) then load remix and load info and it will have another career from the original game and it will come with all the cars that you had before(I don't know about the money though)
In San Diego Take The Big Jump Onto The Aircraft Carrier With Full Speed And Boost. If You Jump High Enough You Should Be Able To Land On A Platform.
