I have NeoOffice 3.1.2, and it won't open a Numbers document - at least not automatically. NeoOffice presents all the formats it knows how to open, and asks you to pick one. There are a lot of formats, and Numbers doesn't appear on the list (far as I can see)... so my advice is don't bother with NeoOffice at this time.
Try the iWork trial. You can then "Share" it to an Excel format so you can continue to work with your preferred application. Just to save you time re-posting..... When you have your document open in Numbers, don't do a "Save As" to get an Excel format, you "Share" it.... it's pretty straightforward from there.