Too many variables to consider... it could depend on how many people live in your area, how far away the Apple Store and Best Buy actually are, how high is the demand in your area, how well did the WiFi unit sell there, how much stock will your local stores get, etc...etc...
It's anybody's guess at this point... Personally I'm trying my luck at Best Buy and I feel pretty confident I'll have one on Friday (of course I did take the day off with an understanding that I may be waiting in line for 5+ hours,
)
One good thing about trying to find it at Best Buy though is that it really hasn't been advertised that Best Buy will even be selling them on Friday... if you aren't actively searching for iPad news or paying much attention to it, you would probably think that only Apple Stores carried them... maybe... hopefully... lol