SSI Web supports a documentation standard called XLIFF, which is basically a coded document that has a variable name (Question1Header, for example), a source text "What is your gender?" and then a spot for a translation text. You can program up your survey in English and get the conjoint set, skip logic, etc. Then you can save a copy of the study (conjoint design and all), export out an XLIFF file to send to a translator, then import the XLIFF file into the copy of the study. Anywhere that there is a translation text, SSI Web will overwrite the original source text for each variable and you'll have a copy of the study in French.
You'll then field two copies of the survey, but since the questions are the same and the conjoint design is the same, you can combine data files together. In version 8 this is very easy since you can get a CSV file of the data from the admin module, do something like add 1,000 to the French respondent numbers and maybe add a country segmentation variable, and then import the data via the Field menu.