This functionality is not supported in the Q1 2012 release, however in later internal builds we exposed the DropDownList Popup options upon the list initialization. With it, you can easily force the DropDownList to open always up ( though screen boundary detection will come into effect if there's not enough space. To do this, download the latest internal build and use this DropDownList initialization:
position: "bottom left",
origin: "top left"
You'll have to adjust the styles a bit.
the Telerik team
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