I don't envy you with some of this advice.
Get reliable advice from respectable pro, either a gardener or a landscaper.
Do you want to kill all the vegetation and plant hundreds of bulbs that bloom for a day (daylilies) and have to be mowed in a month, leaving you with the same problem?
Are you willing to mulch every year, and will rain wash it into the ditch?
Does an annual that has to be reseeded or cut back to rebloom really help?
Will anything you plant be dense enough that you don't have to pull or spray intermittent weeds?
Those gardens you see on TV look and sound great, but they're a lot of work keeping out weeds. Most are in a closed or at least urban environment, rather than in the open or rural area where weed seeds spread from everywhere.
Will you spend a half hour with a string trimmer or mowing up and down?
How about risking loss of traction or a belt slipping going down the hill and sending you into the road?
Many folks, like me, know of guys in our area that have died or been seriously injured when their lawn tractor rolled on banks and hills like yours and worse.
Are you willing to spend more on a piece of equipment than it would cost you to have someone do it for the rest of your time?
I have over 20 years of actual experience on hills much worse than yours.
Above is what I've experienced, not something I think might work. A walk behind mower is the fastest, easiest and safest solution I've found.
Still, I'm no pro, so I would ask one.