If I could learn to speak English fluently, I would be able to have some great conversations with all the foreigners who visit Japan.
この場合、次のような言い方ができますよ。
ーIf I could learn to speak English fluently, I would be able to have some great conversations with all the foreigners who visit Japan.
「英語が流暢に話すことができたら、日本を訪れる外国人と話が弾むだろうに」
to learn to speak English fluently で「(努力して)英語を流暢に話せるようになる」と言えます。
ご参考まで!