The "Align on decimal" feature in tables are really very useful. Therefore, in portuguese we use a comma as the decimal separator.
In future releases, should be a good idea to include in the document configuration some place to determine these regional configurations. There are also, other things to hangle. E.g. I always include the "icomma" package in the preamble when writing a document in portuguese. It would be great if LyX handles this configuration automatically for me. Regards, --- Diego Queiroz