Yes. Always. Even if there's only one candidate.
By voting you endorse a person, an idea, a governing approach to making things better ...
... and/or making them less worse than they would otherwise be, tbh.
More, turning out shows the candidates you care about how your city/state/country is run.
@NiveusLepus
And this seems harsh to some, I know, but if a person doesn't perform the least they can do to make things better, I really don't want to hear their complaints about how fucked up things are.
Your vote matters even if it does nothing more than contribute to the political zeitgeist. Even the most venal, phoning-it-in elected official pays attention to what will get them reelected.