The short answer is, if you don't include retina support for your game, then it will not look crisp on a retina display. You can turn off retina support, and use the SD graphics, and it will work, but it will look blurry.
We did not include retina support for Cow Trouble, but since the majority of our art was pixellated, there were some tricks we were able to use to keep the graphics from being as blurry as they would have otherwise been. We made sure to position all of our objects exactly on pixel boundaries and used a 2D projection. However, there's not really much you can do for text...it is going to be blurry no matter what you do.
Really, you should consider adding retina support to your game. Retina devices are here to stay, and in a couple of years there will not be many non-retina devices left. Instead of creating your art for the non-retina display, and then double-sizing it for retina, you should consider creating your art specifically for the retina display, and generating assets scaled to 50% for the non-retina display. If you are planning on using sprite sheets, then tools like Texture Packer have options to export scaled down sprite sheets, which will make life easier. It's also not too difficult to write a build script to automatically create scaled down assets.
Also, if you do plan on including retina support, it would probably be a better idea to use Apple's @2x suffix for your assets, rather than the -hd suffix (see http://www.cocos2d-iphone.org/forum/topic/28289 for a discussion about this). Duckwit even touches on the fact that it's possible to make non-retina assets look crisper on a retina display if you are using pixellated graphics.
