Up until a couple weeks ago, I wasn't aware that Working Space or Color Profile settings in photoshop mattered. As a result I ended up spending a whole day in the print shop adjusting my colors after conversion, and then calibrating to the printers. I managed to get away with only a couple color-sensitive pieces print badly.
The technician told me that regardless of whether or not I intend for the work to go to print, I should be working in Adobe RGB from the start. Later, I can convert to sRGB for web/common use without shifting colors. Or something along the lines of that...
Anyways, moral of the story: Kinkos suck, don't neglect your print technicians! Subtle differences in hue/tone that show up on your beautiful mac monitor probably won't come out in print!
I'd rather work in ECI-RGB colorspace, as it is slightly bigger than the Adobe RGB space and thus enables you to work with more values. You should also keep in mind that you will be converting to CMYK anyway, and that CMYK colorspaces are FAR smaller than RGB spaces.