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Contrary to the tone of many of these response, I would not hesitate to try a 24" print. I would uprez in photoshop or print out of LR. Both are better at this than we often give them credit. It is important to sharpen after the uprez in photoshop, so that assumes you have access to a file that hasn't been ( over ) sharpened already. I would uprez to a resolution that made my printer happy, 360dpi for epson, 300 for canon.
Most people will be very happy w a large print of an image they like and will not care if it doesn't look perfect at 12", though im not saying this wouldnt produce a perfectly nice print. We get hung up w rules that are overly restrictive. A lot of people believe canvas works well at lower resolutions than paper prints, so that is another possibility.
FWIW, I print large most of the time w 20x30 my normal print. Yes, I prefer large files, but I have lots of older images produced w 6-12 Meg camers, and 16 x24 images are quite good when prepared properly.
I would encourage you to try it before you assume it won't work well. Good luck.