Definitely negotiate and try to get the best price you can. This is a good time of year to buy a rag-top, so use that to your advantage. I suspect that is the gist of some of the earlier posts.
But keep in mind that an '02 S with low miles is a very desirable car. Especially if it has the "important" options. Does it have PSM? How about Litronics? Litronics were standard on the second half of the model year. Do your homework and know what your buying.
Excellence magazine published this range for an '02S (value in 2007):
low 20195 high 30738
You need to decide where this car with 21K miles fall in this range. What if it has litronics, PSM, low miles, impeccable sheetmetal, good tires, nice softtop/rear window, full service records, etc.? Well, you get the idea.
Check out this link for some specific example of what folks are paying:
http://986forum.com/forums/showthread.php?t=12310&highlight=excellence