Most videogames only cater to the English market. As far as I know, all of the 'Speak' options are dubbed in each country's version, with the exception of the non-language specific noises like growling and chanting.
To prove it, here's the japanese intro FMV;
http://www.youtube.com/watch?v=349BQLGk-vQ
It sounds like the Sligs have really high pitched voices in the Japanese games for some reason
You can hear them at 0:10 in this video;
http://www.youtube.com/watch?v=bsAyd...eature=related
Gamefaqs doesn't have a Japanese listing for Abe '99 (neither does Wikipedia), so my guess is that they never made the PC port (I also think that Abe '99 might be quite rare, since it's expensive on the site I saw today [$177]).