I don't think that light from outside is going to be an option in the places I will be shooting this. There are likely to not be any windows at all as it is going to be done in band rehearsal rooms. Have you seen any of these places? I've spent a significant portion of my life in them and they are almost all windowless horrible dumps (or at least the ones my band practices in :-)) So, I don't think the mixed lighting can be avoided completely.
Ah, yes. In that case, I'd just bring enough strobes that you can ignore the ambient lighting. The strobes will very easily be at least 4 stops brighter than those dreadful fluorescents, and the ambient lighting will become irrelevant as long as your shutter speed is faster than, say, 1/30 sec., and you could even get away with slower, but there wouldn't be any reason to. Depending on the look you're after, you might want an edgier film than Portra 160NC, which I originally suggested. Ektar 100 will give you more saturated color.