In general publishing fiction on Hubpages is fine. Just make sure that you follow the terms of service and that you pass Google's Adsense qualifications. If not, you could wind up with your hub being flagged. Most writers don't seem to be publishing anything overly raunchy though.
It is noteworthy, however, that fiction and poetry doesn't tend to rank as well in Hubpages or Google, and you probably won't make a lot of money in Adsense earnings from fiction on Hubpages.