Welcome! It really depends on the game, though the vast majority have japanese text to some extent. I personally don't speak or read japanese, but have still been able to find more than a few games that are completely playable. Other games I need a walkthrough to get me through certain parts. And some games are completely unplayable.
I say get one, and start off with some games like Battle Heat, Last Imperial Prince, Boundary Gate, Galaxy Fraulein Yuna and maybe Power Dolls FX.
If you have the money, the best, most action oriented games are Zenki FX, Chip Chan Kick, and Super God Trooper Zeroigar. All are very expensive, but require no knowledge of japanese, and are fantastic games!