http://www.cdjapan.co.jp sells authentic Japanese DVD's. The main reason I don't support bootlegs is because the money goes to the bootleggers, not the creators who worked so hard to create the show for your enjoyment. This is one of the biggest reason anime is so expensive.
About subtitles: Your DVD remote should have a button on it that toggles the subtitles on and off. If they're HK bootlegs, it's possible the menus will be in English. I've never bought an HK DVD so I wouldn't know.
One thing you should know about HK DVD's: HK DVD's are known to sometimes have bad video quality, sound, and subtitle translations.