Um......
i dont hav a good well expression on english writing but pls let me try to help out of this .....
U will not see all car unlocked unless u have played to grade50 at japan as your home town, grade50 at euro as home your home town , & grade50 at north amer... as your home town.( i think noone will does it like that!?)
for your case,When u reach grade50,U can buy any unlocked car from auction house ,but u may not see them in your garage after u bought it!
change your region now.(of couse hav to pay $$$).then u'll see them show up again ^^
For the saving money reason for this game , i think u better play EuROpean as your region untill grade50 1st .then u can get more discount to buy euro cars ( euro cars realy cost alot $$$). but u'll still having fun wherever u start this game ^^
I hope it helps.