I just stumbled on this and given that I juice and grow my own grass (Kamut, actually), I thought I'd respond.
Sim is quite right; grass fiber is a horror to the human digestive tract. Think about it--ruminants need to process it twice and their systems are actually designed to handle the stuff. I know of people who claim to consume cereal grass in its entirety but given how easy it is to get sick just by drinking too much of the juice, I'm skeptical.
That said, a wheatgrass juicer is absolutely the best way to go (mine's manual) but it's possible to blend it up with some water, after which you could either press is through a fine sieve or run it through a nut milk bag. Either way, you'll be discarding the pulp. As to freezing, it's not a great option if you're going to actually juice the grass (renders it very soggy) but it's fine for blending. Freezing kinda lyses the cell walls but other than that, the chlorophyll isn't altered and the enzymes should be in pretty good shape, too.
Karen3 is also correct that cutting the grass into smaller pieces is a good idea. People who process it in their Vitamixes do it for the very same reason. You don't want to deal with trying to remove grass that got wrapped around a blade shaft at high speed.
