Hi Rajesh,
Same problem for me, currently I created one global blueprint (so shared between my different group) and associated a vDC for each group.
In SelfService portail, my user see 3 blueprint, each one is reserved to a specfic group , therefore each one reserved to a vDC.
Regards,
EDIT:
Or you just have to check box "Allow user to specify reservation type" in build information of your vAPP vCloud Director blueprint, but allocation model will appear not the name of each vDC