Más vale que salgas temprano si no quieres llegar tarde.

Más vale que is an idiomatic expression meaning you’d better or it’s better that. In this sentence, Más vale que salgas temprano means You’d better leave early.

It often sounds a bit stronger than a simple suggestion. It can imply this is the sensible thing to do if you want to avoid a bad result.

Because más vale que normally takes the subjunctive.

• salgas = present subjunctive
• sales = present indicative

After expressions like más vale que, Spanish uses the subjunctive because the speaker is giving advice, a warning, or expressing what should happen rather than stating a plain fact.

So:

• Más vale que salgas temprano = correct
• Más vale que sales temprano = not correct

Salgas comes from the verb salir.

First, take the yo form of the present indicative:

• yo salgo

Then use that stem for the present subjunctive:

• yo salga
• tú salgas
• él/ella salga
• nosotros salgamos
• vosotros salgáis
• ellos salgan

So salgas is the tú form of the present subjunctive: that you leave.

Yes, you can.

• Más vale que salgas temprano = more directly aimed at you
• Más vale salir temprano = more general, like It’s better to leave early

Both are natural. The version with que + subjunctive feels more personal and direct. The infinitive version sounds a bit more general or impersonal.

Because here it means if not:

• si = if
• no = not

So:

• si no quieres llegar tarde = if you don’t want to arrive late / if you don’t want to be late

By contrast, sino as one word usually means but rather or except.

For example:

• No quiero té, sino café = I don’t want tea, but rather coffee

That is a completely different structure.

Because llegar tarde is the normal Spanish way to say to arrive late or to be late getting somewhere.

Examples:

• Llegué tarde = I arrived late
• No quiero llegar tarde = I don’t want to arrive late

English sometimes says be late, but Spanish often expresses the idea with arrive late when talking about getting somewhere after the expected time.

Here, temprano is an adverb meaning early.

It modifies the verb salgas:

• salir temprano = to leave early

Spanish often uses words like temprano and tarde directly as adverbs, without needing something like English -ly.

Because Spanish often leaves out subject pronouns when the verb form already makes the subject clear.

In this sentence:

• salgas already shows tú
• quieres already shows tú

So tú is unnecessary unless you want emphasis or contrast.

For example:

• Más vale que tú salgas temprano...

This would sound more emphatic, as if contrasting you with someone else.

In más vale, the expression is basically fixed. It comes from the verb valer and literally relates to the idea of being worth more, but in modern Spanish más vale functions as an idiom.

So learners should usually treat más vale as a set expression meaning:

• it’s better
• you’d better

You do not normally change it to match the person being spoken to.

Usually, yes.

• Deberías salir temprano = You should leave early
• Más vale que salgas temprano = You’d better leave early

Más vale que often sounds more like a warning or strong recommendation, especially when there is a consequence mentioned, as in this sentence:

• ...si no quieres llegar tarde = ...if you don’t want to arrive late

So the full sentence has the feel of: You’d better leave early, unless you want to be late.