i have blended wheatgrass with some success. but remember, the reason cows can eat grass is that they have four stomachs. during its journey thru these stomachs the grass is slowly fermented and broken down over time. we have only one stomach, which is why eating grass is difficult for humans. the cellulose wall of grass is very tough and difficult to break down, thats why we juice it - the powerful gears of the juicer break down the wall and extract the yummy juice, something our stomachs are not capable of.
so i think juicers are better at extracting the juice from grass, but blenders will also have some use. i must say tho blended wheatgrass is not very palatable. the texture isn't that great for some reason.
i would recommend a really strong blender, a vita mix if possible. good luck, let us know how it goes.