If your target output is NTSC, then ideally you would film in NTSC, not PAL.
The thread I pointed you at discusses many of the conversion issues you will need to investigate for cross-format work. One of the posters seemed fairly content with using Premiere to do the conversion, but better quality is achievable by using a good format converter on the AVI before editing in Premiere in the target format. Optimum workflow depends on your final target – the bigger the output frame size and/or displayed screen size, the more the quality of conversion becomes important.
A forum search, as I suggested, will generate even more useful information.