Sugizo speaks fluently enough now to be able to travel without a translator, around 10 years ago when he was in London recording his first solo album he was a little bit ropey with his English so needed people around him to bridge the communication barrier.
Toshi speaks English at a conversational level, but hasn't really had the practice that Yoshiki has. There are many clips of Toshi speaking in English, such as the 2008 reunion lives when he speaks to Richard Fortus. His voice in English sounds... kinda strange XD
Hide's English was a little bit suspect at first, but he spent a lot of time in Los Angeles for X Japan and his solo project as well as owning a house therr, but his pronounciation of English words was never very strong. His English lyrics in Zilch kinda stand as testament to this.
As far as I'm aware Pata can speak very few phrases in English, Heath is a little more rounded than him and has sung in English before on several occasions for his solo project, but neither are particularly strong speakers to say the least.
As for Taiji, in interviews when he's been asked to speak in English he's always seemed either unable or reluctant, but I've seen at least one video from his live in LA last year that proves he can at least communicate with people in it.