Learn Spanish (Latin America): Subo las escaleras cada día.

You would add ojalá que and change the verb to the present subjunctive. Because subir is an -ir verb, the 'yo' form in the subjunctive is suba. The new sentence is: Ojalá que suba las escaleras cada día.

Does subo only mean 'I go up'?

It usually means 'I go up' or 'I climb' (like stairs or a mountain). You will also hear the infinitive subir used for getting onto a bus or train, and even for uploading a file to the internet!

Could I use todos los días instead of cada día at the end of the sentence?

Yes, absolutely! Cada día literally means 'each day,' while todos los días means 'all the days' (every day). They mean the exact same thing in this context and are completely interchangeable.

Why is escaleras plural here?

In Spanish, a flight of stairs is usually talked about in the plural as las escaleras, just like we say 'the stairs' in English. The singular form, la escalera, can mean a single staircase or a ladder.