“I would set it for... 5:30?”

You have to wake up early tomorrow to go to the airport for your vacation. Your husband is close to your alarm clock. You want to tell him what time you think you should wake up.

I would set it for... 5:30?

I would (do something)

When you're giving your opinion but don't want to say it too strongly (because you're being polite or because you don't feel strongly about it), you can say "I would ___". Examples of this are:

I would lean toward staying in Spain.

I would go with the higher-priced model.

You often use "I would ___" when you're giving someone else advice, and you're not the person making the final decision.

set (an alarm) for (a time)

"Setting" an alarm means choosing what time the alarm is going to go off.

Give the time that you choose with "for":

Set it for 30 minutes from now.

I usually set my alarm for 9:00.