You can be very passable in your appearance, but if you speak in a masculine voice you've just outed yourself. It amazes me how many transsexual women speak in a masculine-sounding voice.
They'll spend thousands on hormones, electrolysis, surgery, etc. but won't make the effort to retrain their voices. If you don't mind getting sir'd on the phone, or even in public, go ahead and talk like a man. But if you want to pass as a woman your voice is important.
Whether we like it or not, we're all ambassadors for the trans community and people will often base their opinions of us on first impressions. If you speak in a male voice, not only will there be incongruity between your voice and appearance, but it will tend to make people relate to us more as drag queens and crossdressers, an image we need to get away from.
Any male voice can be retrained. Don't be discouraged if you're starting with a baritone! For proof that your voice can be changed, try talking in falsetto. Obviously, it sounds silly and I don't recommend talking in falsetto, but it shows even the deepest voice can be raised.
Just like your walk, you're unlearning years of doing something in a masculine way. You're retraining your throat muscles. It was two-and-half months before I started getting "ma'am" on the phone and it may take a year, or more, before your voice sounds good in all situations, like yelling.
Will hormones make your voice higher? Unless you started HRT at the onset of, or early, puberty before your voice changed, hormones will have no effect on pitch, though estrogen will tend to soften the voice.
What about vocal surgery? That's an option and can take the worry out of whether you'll get clocked when you speak. I know three trans women who've had vocal surgery. Two sounded good and one didn't, she sounded raspy. As with most surgery, the outcome of voice surgery isn't certain. Explore your options and educate yourself about vocal surgery before deciding.