I assume that they want to see something that verifies that you can understand form visually-it really doesn't matter what you draw as long as it represents your ability to recognize line as it vanishes, proportion, scale, etc...
For my portfolio, I submitted free hand sketches I had to do for an Architecture history class in undergrad. I had visited several famous places in Europe and I drew pictures of photographs. I am also from Nashville, TN and there is a replica of the parthenon there, so I went and drew it one day. If you would like to see an example I am more than welcome to show you...but I wouldn't try to use it because I do have the original!

I'll preface this by saying I'm not an admissions committee, so I don't know exactly what you might need for a successful application. I'm also not sure how quickly a person can learn how to draw. That being said, grasping the basics of perspective (1- and 2-point) can be done pretty quickly. You might look at the book Architectural Sketching and Rendering: Techniques for Designers and Artists, ed. Stephen Klimt, if you want to try some exercises.

In my first drawing class, the teacher set up a still-life of chair and box on a checkerboard carpet, which was incredibly effective in helping us establish planes, parallels, etc.. Then he added things--a wrinkle in the carpet, a lamp on the box, a glass. It was an excellent exercise and sometimes when I'm looking at an object wondering how to draw it, I visualize it in the same setting. It helps me establish planes and parallel lines.

Like mjh, when I'm going to do a watercolor of a site, I usually take a photo and draw more from the photo and less from the scene in front of me.

I'm guessing style and spirit is going to influence a committee more than absolute accuracy of detail and space.

buy a book called visual notes

buy a book called visual notes

Here's an interesting exercise that might help you loosen up your drawing muscles: do a "contour" or "outline" drawing. This is where you put your sketchbook in front of you, put pen to paper, and "trace" the outline of an object without removing your eyes from the object, without looking at your hand or the paper. It's a blind sketch, and it forces you to really see the physical properties of the object as well as to understand the way 3-D objects can appear to exist in 2-D. It also leads to some interesting, almost recognizable drawings, that aren't about true representation, which might help you to not worry so much about whether they are "good" drawings or not - they are tools, not finished products, but they tend to look cool.

Oh, yeah, and drawing a contour drawing of your hand (the other hand, not the one you are drawing with) looks really cool, and you can do it during boring lectures in class!

my guess is that content is not an issue.

liberty is talking about an exercise that comes directly from "drawing on the right side of the brain" (i believe that's what it is called, but don't trust me). it is a good introduction to ways of approaching art for someone who doesn't do it already. Worth looking at, but take with a grain of salt like all how-to books.

when i look at the drawings my 5 year old does i am always impressed with their freshness and her inherent willingness to fail (ie, she is not expecting to be judged so doesn't care). When I look at the work of contemporary artists I admire it is usually the same thing that attracts me, whether it is drawing, sculpture, video, whatever. getting to that point is very hard but if you are just learning to draw now, maybe keep it in the back of your mind as something to aim for. It will certainly stand out in a portfolio much more than merely good craft.

right, that artsy enough for you?