I've been going to the cafe just to talk to him/her.
I've been going to the cafe just to talk to him/her.（彼/彼女と話すためだけにカフェに通い続けている）
Just because I want to talk to him/her, I've been going to the cafe.（彼/彼女と話したいがためにカフェに通い続けている）
I visit that cafe frequently because I want to talk with a guy who works there.
この場合、次のような言い方ができますよ。
ーI visit that cafe frequently because I want to talk with a guy who works there.
「カフェで働いている男性と話したくて、カフェに通い詰めている」
to visit XX frequently で「XXに通い詰める」と言えます
ご参考まで！
日本 
カナダ 
