Here are two clubs in Tsukuba.
Club: つくば囲碁センター Tsukba Igo Center
Address: つくば市竹園2丁目7-11 Tsukuba City (shi), Bamboo Garden (Take no sono, or Chikuen), Block (Chome) 2, 7 - 11
Telephone: 0298-50-0255
Club: 三須昇碁会所日本棋院支部 Misu Noboru (person's name) Go Club (gokaisho), Nihon Kiin branch (shibu)
Address: つくば市観音台1丁目2-2 Tsukuba City, Pedestal of Kannon Buddha (Kannon dai), Block 1, 2-2
Telephone: 0298-37-0148
Since you have time, I would suggest writing to the clubs in English or German a month or two before you go. I think that you will find them quite hospitable.

If you can't do the addresses in kanji, something like this would probably be fine, although it might cause a little delay:
Tsukuba Igo Senta
Tsukuba shi
Take no sono
2 chome 7 - 11
Misu Noboru Go Club, Nihon Kiin shibu
Tsukuba shi
Kannon dai
1 chome 2 - 2