Well, you can't go wrong with playing Hotel Dusk 1 first. It's an amazing game, and not too hard to find, and if you're interested in this game, then you can't go wrong with Hotel Dusk 1.
However, there is no need to play the first game before this one - the story hints at a few things from there, but you don't need any knowledge of the first game to enjoy this, so if you can't find it, or would like to enjoy the little tweaks they added to this game (which aren't that many), then just go ahead and play this.
Oh, did I mention that while you play, the current actions of the game are added to a complete novel in the game? It's said that those contents even change depending on what you do. So you can always read that novel to remember what happened (but there is a much shorter "tl;dr"-version avaible, too, which I honestly prefer).
I can't praise the game enough. I'm not done with it yet, but honestly, if it were to only display "You're an asshole" at this point and make my DS explode, taking parts of my body with it, I'd still think that it's a great game and I'd still recommend it. I love how it keeps you in the dark with most things for so long (of course, all things are revealed... I guess? They did that in the first game :P), and I love how it's impossible to guess what happens next and who's behind all that mysterious stuff that happens, and I love how this game is able to make even the most unusual characters likeable. (All that is something that you can say for the first game, too, by the way)