The other obvious club is Athletic Bilbao who only field players from the Basque region in Spain. Outside of those two I didn't know what to expect. Here's what I came up with. (The percentage indicates home grown talent on each squad)
|100%||Gwangju Sangmu Phoenix||Korea|
|100%||5 clubs: Sport Recife, Ipatinga, Coritiba, Goias, Portuguesa||Brazil|
|100%||Deportivo Saprissa||Costa Rica|
|98%||Club Atletico San Lorenzo de Almagro||Argentina|
|95%||Central Coast Mariners FC||Australia|
|93%||FC Naftovyk Okhtyrka||Ukraine|
|70%||FC Tom' Tomsk||Russia|
Of the bigger clubs in the world, São Paulo has the highest percentage of home grown talent that I found, with the entire squad being Brazilian except for Reasco, who is a DF from Ecuador.
Japan, Korea, and Australia's leagues have a very high percentage of home grown talent, with most of the outsiders being Brazilians. I didn't run the numbers, but I would guess that these three leagues use about 85%-90% home grown players.
As an MLS fan, it was interesting to see the Houston Dynamo so far down the list. It really shows how international the league is when the most "American" team in the entire league has nearly 20% international players. DC United is right around 50/50 with their current roster.
Now that I've done this list, I plan to take a look at the opposite end of the spectrum, and find the clubs using the least amount of home grown talent. In England, Arsenal is the club everyone talks about as being "foreign", it'll be interesting to see if they top the list of clubs with the highest percentage of foreign players.