'5pm is a good time to talk for me'
Here's what my ear recommends for Mexico -- I don't know about other places. It would be more polite to pose a question. Culturally, others will understand that even though you are expressing yourself in a question, you are still making your preference understood. I have heard people from various parts of the Caribbean and Africa use this approach when talking in English.
This is similar to something we do in English -- notice that "It would be more polite" is softer than "It is more polite."
Thus, a couple of simple versions would be
¿Podemos hablar a las 5?
¿Podríamos vernos a las 5?
¿Te puedo llamar como a las 5? (Can I call you at around 5?)
If you know the person well:
¿Me llamas a las 5?
Te llamo a las 5, ¿está bien?
¿Vas a estar disponible a las 5?
Here are two verbs that would be a bit more precise:
I'm not finding the right definition in Linguée or DRAE, unfortunately. You would use this verb to say that a certain shirt fits you well (in terms of size) or that it combines well (in terms of color) with a certain pair of pants or that it suits you (in terms of style). In scheduling, it would mean that a certain time would be comfortable for you.
Thus, the following would be a bit more formal (but not to the point of being stuffy) than the earlier proposals:
¿Lo puedo llamar más tarde? ¿Le quedaría bien a las 5 de la tarde?
¿Podríamos platicar [conversar] más tarde? Le conviene [convendría] llamarme como a las cinco? (Could we talk later? Would around 5:00 be convenient?)
You can also express regret and say when you'll free up:
Disculpa, ando un poco apurado/a ahorita pero voy a estar disponible a partir de las 5. (I'm sorry, I'm in a bit of a hurry just now but I'll be available any time from 5 on.)