Contrary to Erica's suggestion (Erica, please forgive me!) I advise you NOT to convert your material BEFORE the edit.
You might have, for example, to convert 20 sixty minute shooting tapes whereas, AFTER the edit, only 52 minutes TOTAL ( if your doc is a one-hour-long format) or even less than that if part of it was shot in NTSC.
Also, if you're only shooting in Italy, it'll all be PAL. If you'll be doing some shooting in US, shoot in PAL (if you can) or shoot NTSC. It won't make any difference as you do a rough cut; convert at the end and splice it all together.
If you check B&H you'll notice that – in a worst case scenario – converters are cheap today.
If you do a search on the B&H website www.bhphotovideo.com using the words "PAL NTSC standards converter" you'll find several models listed including the AV Toolbox CDM-660 Standards Converter that costs only $179.95. There are several other models that cost between $359 and $539.
I don't see why the cheaper one couldn't do the job. In any case, I imagine – as a worst case scenario – that it would be cheaper to buy than convert all the tapes.
I'd advise you – for the moment – not to keep worrying about what comes next. Concentrate on your upcoming shoot in Italy and enjoy yourself.
If you MUST worry about something, worry about finding an excellent editor! :-)