This requires some attention, there are two options I think:
1) Separating the data in a way that will enable you to only show the data that either the user himself, or users from (for instance) the same company have entered into the database. This implies that a French user will never be able to see input from English users 2) Translating the input of the users is another option, although this will require a lot of work I suspect.
The easiest however (and probably the way most larger multinationals will handle this) is to make every user use English