A printer is asking for a 300 dpi jpeg. I have set the image size to the correct printing size but what resolution do I set the ppi in photoshopCS2 to for 300 dpi. Also when saving a jpeg there is a box at the bottom saying Size which is 56.6 Kbps do I need to change this as it doesn't seem to change the image size?
PPI means "pixels per inch," and is a web display measurement.
DPI means "dots per inch," and is a print measurement.
If your Image Size dialog box reads "300 pixels per inch," you're fine. However, if you're starting at less than that, most likely you cannot arbitrarily make the PPI larger without sacrificing quality. (Depends on how far you're sampling up and what the image is. 266 → 300: probably okay. 72 → 300: ain't gonna happen.)
When you're saving the JPG for print, you shouldn't be using the Save for Web option. That's why you're getting the modem speed. That number (56.6Kpbs) is telling you "this is how many seconds your image will take to download to the user's browser at this given speed." It's not relevant to you in this context. Use Save As instead.