A few options come to mind. It's not clear whether your final output will be as vector or bitmap, but either way you could just use imagemagick: translate the latitude and longitude into coordinates relative to the size of your image and then drop a symbol in at that point. You can then output the final image in whatever form you like (including eps, with help from ghostscript, but afaik only bitmap files in eps format, not true vector files).

or if this for the web, it might be easier just to output a set of coordinates and read them into a flash movie, with a bit of scripting there to put symbols in the right places.

if the goal is vector artwork for print, it's a bit harder. You could look into the various pdf modules, which will give a file that illustrator can read natively but which you'd have to translate to get into anything but the latest version of quark.

a better option might be to use adobe's the W3C's SVG format. There's a set of modules that will allow you to build the xml-based files it uses: it looks ideal for symbol placement, but would probably need to be combined with readymade files if complex backgrounds are involved (which ought to be easy, given the nested structure of the file). Again, translation would be required before use in print.

SVG boosterism from adobe, more restrained overview from xml.com.