@jchny2000 Have you considered Belted Galloway? I've occasionally seen them and heard great things about them. They're naturally polled, have marbled beef, can be milked, are generally sweet natured, still gave maternal instinct, and are about the size of Hereford. Hereford might be cheaper because they're omnipresent, but I'm no cattle expert. Galloways look like Oreos and are known to thrive on nasty winters and forage other breeds shun, but Herefords are popular globally because they're also a tough, adaptable breed.
I've heard less awesome things about Angus. My mom used to show cattle in 4 H, and she said that you could whack a Hereford across the head with a 2x4, and it would just look at you, but if you did that to an Angus, prepare to die, pretty much. All of the Hereford I've met have been pretty docile--even with crazy, interloper teenagers in their pastures. Never met an Angus in person, but I've heard they've got good memories and a better brain for strategy. However, even Hereford can be taught dressage, so I don't think they're stupid so much as docile.
If you want inspiration, you can look up saddle cattle. I can't find that dressage video, though other people have posted videos and pictures of riding both beef and dairy breeds.