Yes, LEED documentation should be in English.
I would not go through the effort of translating product data sheets. In most cases would the relevant data be in Arabic numerals that anyone could read? Perhaps you could make some notes on the PDF pointing out the relevant information and making any quick translations you think would be helpful for the reviewers.
In most cases, data sheets serve as back-up documentation in case a specific credit is reviewed in detail—they don't serve as primary credit documentation, which is in the LEED Online forms, in English.
I could be wrong, though—I'd be curious for others with experience on this to comment?