たらいい・といい

It would be nice if, It would be good if, Should, I hope

私わたしもあんなに速はやく走はしれたらいいな。

It would be nice if I could also run that fast.

Explanation

「たらいい・といい」 has 2 uses

Says what you hope for, 'it would be nice if…', often ending in 「な」 or 「ね」: 「合格するといいね」.

毎日まいにち、好すきな番組ばんぐみが見みられたらいい。

It would be nice if I could watch my favorite TV show every day.

来年らいねんは海外かいがい旅行りょこうに行いけるといいね。

It would be nice if we could travel abroad next year, right?

Gives easy advice, 'you could just…': 「聞いてみたらいい」. To ask what to do: 「どうしたらいい？」

自由じゆうにしたらいいでしょう。

Just do as you like.

文句もんくを言いわないで！どうしたらいいのか教おしえてよ。

Stop complaining! Tell me what would be good to do!

Examples

1Wishing for something

毎日まいにち、好すきな番組ばんぐみが見みられたらいい。
It would be nice if I could watch my favorite TV show every day.
来年らいねんは海外かいがい旅行りょこうに行いけるといいね。
It would be nice if we could travel abroad next year, right?
明日あしたと明後日あさっても晴はれるといいですね。
It would be nice if the weather were clear tomorrow and the day after, wouldn't it?
僕ぼくもイルカみたいに上手じょうずに泳およげたらいいのに。
I wish I could swim well like a dolphin. (it would be good if...)
いつか一緒いっしょに日本にほんに行いけるといいな。
I hope that I can go to Japan with you someday. (it would be good if...)
いつかまたどこかで会あえたらいいね。
I hope that we can meet each other again somewhere, someday.
昔むかし大好だいすきだったお店みせ、まだやっているといいな。
I hope the restaurant (shop) that I loved is still open. (it would be good if...)

2Suggesting what to do

文句もんくを言いわないで！どうしたらいいのか教おしえてよ。
Stop complaining! Tell me what would be good to do!
日本語にほんごを上手じょうずにしゃべれるようになりたかったら、日本人にほんじんとしゃべったらいい。
You should speak to Japanese people if you want to improve your Japanese conversational ability. (it would be good if...)
自由じゆうにしたらいいでしょう。
Just do as you like.
失敗しっぱいしてもいいからやってみるといい。
It doesn't matter if you mess up. It would be better if you just tried it.
どの道みちを行いったらいいのかもっと詳くわしく教おしえてください。
Please tell me in more detail which way would be good to go.
あの人ひとに聞きいてみるといい。何なんでも答こたえてくれるから。
It would be good to ask that person. He will answer any question.