I'll leave my house in plenty of time so that I can arrive at the place where we agree to meet 15 minutes early.
この場合、次のように言えますよ。
ーI'll leave my house in plenty of time so that I can arrive at the place where we agree to meet 15 minutes early.
「待ち合わせ場所に15分早く着けるよう、家を余裕を持って出ます」
place where we agree to meet「待ち合わせ場所」
ーI'm always late when I meet someone.
「誰かと待ち合わせるときいつも遅れる」＝「いつも待ち合わせに遅れる」
ご参考まで！
カナダ 
