Sure you can, you can either use file>save as or file>save for web and devices. If you do not see jpg listed as file format in the drop down box, odds are your document is in the wrong mode. Make sure your color depth is set to 8 not 16 or 32. as jpg only supports 8.
Also keep in mind the jpg does not support layers or transparency.
ok thanks. how do i change it from 32 to 8. i saw it in options but i cant find it now