time of week to visit Cappadocia

I don't think the day of the week is going to make much difference in crowding for Cappadocia. It's a major destination for international tourists, and they/we (generally) are not governed much by the days of the week ("if it's Tuesday this must be Bodrum..."?). Yes, I'm sure plenty of domestic Turkish tourists go there, too, and yes, they probably increase tourist numbers on weekends, but I'd guess that's just a drop in the bucket - the percentage of domestic tourists is probably tiny compared to the foreigners. When I was there it appeared to be almost entirely set up for foreigners - it's the only place in all of Turkey I saw prices posted first in US Dollars (along with Euros, Pounds, Yen, Yuan, Won, and Rubles).

Just a guess, but I'd think factors more likely to have an impact on relative crowd sizes there would primarily be the season (summers most busy, winters less busy); and to a lesser degree, worries about world events (I have friends who are thinking of cancelling their upcoming trip to Turkey over vague fears of "unrest" etc., I suspect this same fear is dampening tourism to some degree, at least by Americans - there are plenty of non-Americans going to Turkey).

Tip: Plan to be there for at least 2-3 days, and book you balloon flight for your first morning there (because when the weather does not cooperate, the balloons do not fly; if your first flight date gets cancelled due to bad conditions - and that's quite common - then you have a chance to have your flight rescheduled for your 2nd or maybe 3rd morning there). Late September is probably a good time to be there - not during the full heat of summer, but not too cold (up in the balloon, it gets colder, bring layers). Probably a sweet spot for crowds/weather, too.