So I just saw a 58cm Fuji track frame on craigslist for a decent price.
I'd have no hesitation with buying it except that I'm around 5'11 and my current setup is a 55cm.
Would a 58cm frame for a fixie, (no 60 mile rides, mostly within the limits of DC) be too big for someone my size?

It really depends on how you're built and what your body is comfortable with. I'm 5'11" and very comfortably ride a 58cm Leader 722TS. I have longish arms and prefer a bike with a long top tube.

It's a little too big (given 55cm is your "perfect" size?).

yeah it really depends on your build. like scrod said, he rides a 58 at 5'11" and it suits him. i ride a 58 at 6'2" and feel it runs anywhere from perfect to a tiny bit big for me.

a lot more goes into frame sizing than height.

I am 5'11" and I have always thought a 58 rides too big. A 56 suits me perfectly. Dialed in.

Same height, but all in the legs. I prefer the shorter top tube on a 54 or 55.
You need to check it out for your own proportions.

I have a 55 for my fixed gear, and a 58 for my road bike and I'm 5'11. Neither are uncomfortable, however after riding the fixed gear alot, the road bike did feel a bit big... but it just took me a couple miles to get used to the more stretched out position.

I think my proper size is most likely around 55-56 though...

I stand 6'2" but have very short legs (32" inseam).

A 58 with a set back seatpost would work great for me as it would give me the standover I need.

The Fuji 58 has a standover of 816.5 mm, or 32".

What length trousers do you wear?